  ON ALLEGED "SPONTANEOUS GENERATION," AND ON THE HYPOTHESIS OF PHYSIOLOGICAL UNITS. [The following letter, originally written for publication in the North American Review, but declined by the Editor in pursuance of a general rule, and eventually otherwise published in the United States, I have thought well to append to this first volume of the Principles of Biology. I do this because the questions which it discusses are dealt with in this volume; and because the further explanations it furnishes seem needful to prevent misapprehensions.] The Editor of the North American Review. Sir, It is in most cases unwise to notice adverse criticisms. Either they do not admit of answers or the answers may be left to the penetration of readers. When, however, a critic's allegations touch the fundamental propositions of a book, and especially when they appear in a periodical having the position of the North American Review, the case is altered. For these reasons the article on "Philosophical Biology," published in your last number, demands from me an attention which ordinary criticisms do not. It is the more needful for me to notice it, because its two leading objections have the one an actual fairness and the other an apparent fairness; and in the absence of explanations from me, they will be considered as substantiated even by many, or perhaps most, of those who have read the work itself—much more by those who have not read it. That to prevent the spread of misapprehensions I ought to say something, is further shown by the fact that the same two objections have already been made in England—the one by Dr. Child, of Oxford, in his Essays on Physiological Subjects, and the other by a writer in the Westminster Review for July, 1865. ***** In the note to which your reviewer refers, I have, as he says, tacitly repudiated the belief in "spontaneous generation;" and that I have done this in such a way as to leave open the door for the interpretation given by him is true. Indeed the fact that Dr. Child, whose criticism is a sympathetic one, puts the same construction on this note, proves that your reviewer has but drawn what seems to be a necessary inference. Nevertheless, the inference is one which I did not intend to be drawn. In explanation, let me at the outset remark that I am placed at a disadvantage in having had to omit that part of the System of Philosophy which deals with Inorganic Evolution. In the original programme will be found a parenthetic reference to this omitted part, which should, as there stated, precede the Principles of Biology. If, accepting these alleged cases of "spontaneous generation," I had assumed, as your reviewer seems to do, that the evolution of organic life commenced in an analogous way; then, indeed, I should have left myself open to a fatal criticism. This supposed "spontaneous generation" habitually occurs in menstrua that contain either organic matter, or matter originally derived from organisms; and such organic matter, proceeding in all known cases from organisms of a higher kind, implies the pre-existence of such higher From what I do not believe, let me now pass to what I do believe. Granting that the formation of organic matter, and the evolution of life in its lowest forms, may go on under existing cosmical conditions; but believing it more likely that the formation of such matter and such forms, took place at a time when the heat of the Earth's surface was falling through those ranges of temperature at which the higher organic compounds are unstable; I conceive that the moulding of such organic matter into the simplest types, must have commenced with portions of protoplasm more minute, more indefinite, and more inconstant in their characters, than the lowest Rhizopods—less distinguishable from a mere fragment of albumen than even the Protogenes of Professor Haeckel. The evolution of specific shapes must, like all other organic evolution, have resulted from the actions and reactions between such incipient types and their environments, and the continued survival of those which happened to have specialities best fitted to the specialities of their environments. To reach by this process the comparatively well-specialized forms of ordinary Infusoria, must, I conceive, have taken an enormous period of time. To prevent, as far as may be, future misapprehension, let me elaborate this conception so as to meet the particular objections raised. The reviewer takes for granted that a "first organism" must be assumed by me, as it is by himself. But the conception of a "first organism," in anything like the current sense of the words, is wholly at variance with conception of evolution; and scarcely less at variance with the facts revealed by the microscope. The lowest living things are not properly speaking organisms at all; for they have no distinctions of parts—no traces of organization. It is almost a misuse of language to call them "forms" of life: not only are their outlines, when distinguishable, too unspecific for description, but they change from moment to moment and are never twice alike, either in two individuals or in the same individual. Even the word "type" is applicable in but a loose way; for there is little constancy in their generic characters: according as the surrounding conditions determine, they undergo transformations now of one kind and now of
this complex compound, by operating on another complex compound, such as the dimethyl-amine named above, generates one of still greater complexity, butyrate of dimethyl-amine
See, then, the remarkable parallelism. The progress towards higher types of organic molecules is effected by modifications upon modifications; as throughout Evolution in general. Each of these modifications is a change of the molecule into equilibrium with its environment—an adaptation, as it were, to new surrounding conditions to which it is subjected; as throughout Evolution in general. Larger, or more integrated, aggregates (for compound molecules are such) are successively generated; as throughout Evolution in general. More complex or heterogeneous aggregates are so made to arise, one out of another; as throughout Evolution in general. A geometrically-increasing multitude of these larger and more complex aggregates so produced, at the same time results; as throughout Evolution in general. And it is by the action of the successively higher forms on one another, joined with the action of environing conditions, that the highest forms are reached; as throughout Evolution in general. When we thus see the identity of method at the two extremes—when we see that the general laws of evolution, as they are exemplified in known organisms, have been unconsciously conformed to by chemists in the artificial evolution of organic matter; we can scarcely doubt that these laws were conformed to in the natural evolution of organic matter, and afterwards in the evolution of the simplest organic forms. In the early world, as in the modern laboratory, inferior types of organic substances, by their mutual actions under fit conditions, evolved the superior types of organic substances, ending in organizable protoplasm. And it can hardly be doubted that the shaping of organizable protoplasm, which is a substance modifiable in multitudinous ways with extreme facility, went on after the same manner. As I learn from one of our first chemists, Prof. Frankland, protein is capable of existing under probably at least a thousand isomeric forms; and, as we shall presently see, it is capable of forming, with itself and other elements, substances yet more intricate in composition, that are practically infinite in their varieties of kind. Exposed to those innumerable modifications of conditions which the Earth's surface afforded, here in amount of light, there in amount of heat, and elsewhere in the mineral quality of its aqueous medium, this extremely changeable substance must have undergone now one, now another, of its countless metamorphoses. And to the mutual influences of its metamorphic forms under favouring conditions, we may ascribe the production of the still more composite, still more sensitive, still more variously-changeable portions of organic matter, which, in masses more minute and simpler than It is thus manifest, I think, that I have not fallen into the alleged inconsistency. Nevertheless, I admit that your reviewer was justified in inferring this inconsistency; and I take blame to myself for not having seen that the statement, as I have left it, is open to misconstruction. ***** I pass now to the second allegation—that in ascribing to certain specific molecules, which I have called "physiological units," the aptitude to build themselves into the structure of the organism to which they are peculiar, I have abandoned my own principle, and have assumed something beyond the re-distribution of Matter and Motion. As put by the reviewer, his case appears to be well made out; and that he is not altogether unwarranted in so putting it, may be admitted. Nevertheless, there does not in reality exist the supposed incongruity. Before attempting to make clear the adequacy of the conception which I am said to have tacitly abandoned as insufficient, let me remove that excess of improbability the reviewer gives to it, by the extremely-restricted meaning with which he uses the word mechanical. In discussing a proposition of mine he says:— "He then cites certain remarks of Mr. Paget on the permanent effects wrought in the blood by the poison of scarlatina and small-pox, as justifying the belief that such a 'power' exists, and attributes the repair of a wasted tissue to 'forces analogous to those by which a crystal reproduces its lost apex.' (Neither of which phenomena, however, is explicable by mechanical causes.)" Were it not for the deliberation with which this last statement is made, I should take it for a slip of the pen. As it is, however, I have no course left but to suppose the reviewer unaware of the fact that molecular actions of all kinds are now not only conceived as mechanical actions, but that calculations based on this conception of them, bring out the results that correspond with observation. There is no kind of re-arrangement among molecules (crystallization being one) which the modern physicist does not think of. Premising, then, that the ordinary idea of mechanical action must be greatly expanded, let us enter upon the question at issue—the sufficiency of the hypothesis that the structure of each organism is determined by the polarities of the special molecules, or physiological units, peculiar to it as a species, which necessitate tendencies towards special arrangements. My proposition and the reviewer's criticism upon it, will be most conveniently presented if I quote in full a passage of his from which I have already extracted some expressions. He says:— "It will be noticed, however, that Mr. Spencer attributes the possession of these 'tendencies,' or 'proclivities,' to natural inheritance from ancestral organisms; and it may be argued that he thus saves the mechanist theory and his own consistency at the same time, inasmuch as he derives even the 'tendencies' themselves ultimately from the environment. To this we reply, that Mr. Spencer, who advocates the nebular hypothesis, cannot evade the admission of an absolute commencement of organic life on the globe, and that the 'formative tendencies,' without which he cannot explain the evolution of a single individual, could not have been inherited by the first organism. Besides, by his virtual denial of spontaneous generation, he denies that the first organism was evolved out of the inorganic world, and thus shuts himself off from the argument (otherwise plausible) that its 'tendencies' were ultimately derived from the environment." This assertion is already in great measure disposed of by what has been said above. Holding that, though not "spontaneously generated," those minute portions of protoplasm which first displayed in the feeblest degree that changeability taken to imply life, were evolved, I am not debarred from the argument that the "tendencies" of the physiological units are derived from the inherited effects of environing actions. If the conception of a "first organism" were a necessary one, the reviewer's objection would be valid. If there were an "absolute commencement" of life, a definite line parting organic matter from the simplest living forms, I should be placed in the predicament he describes. But as the doctrine of Evolution itself tacitly negatives any such distinct separation; and as the negation is the more confirmed by the facts the more we Much evidence now conspires to show that molecules of the substances we call elementary are in reality compound; and that, by the combination of these with one another, and re-combinations of the products, there are formed systems of systems of molecules, unimaginable in their complexity. Step by step as the aggregate molecules so resulting, grow larger and increase in heterogeneity, they become more unstable, more readily transformable by small forces, more capable of assuming various characters. Those composing organic matter transcend all others in size and intricacy of structure; and in them these resulting traits reach their extreme. As implied by its name protein, the essential substance of which organisms are built, is remarkable alike for the variety of its metamorphoses and the facility with which it undergoes them: it changes from one to another of its thousand isomeric forms on the slightest change of conditions. Now there are facts warranting the belief that though these multitudinous isomeric forms of protein will not unite directly with one another, yet they admit of being linked together by other elements with which they combine. And it is very significant that there are habitually present two other elements, sulphur and phosphorus, which have quite special powers of holding together many equivalents—the one being pentatomic and the other hexatomic. So that it is a legitimate supposition (justified by analogies) that an atom of sulphur may be a bond of union among half-a-dozen different isomeric forms of protein; and similarly with phosphorus. A moment's thought will show that, setting out with the thousand isomeric forms of protein, this makes possible a number of these combinations almost passing the power of figures to express. Molecules so produced, perhaps exceeding in size and complexity those of protein as those of protein exceed those of inorganic matter, may, I conceive, be the special units belonging to special kinds of organisms. By their constitution they must have a plasticity, or sensitiveness to modifying forces, far beyond that of protein; and bearing in mind not only that their varieties are practically infinite in number, but that closely allied forms of them, chemically indifferent to one another as they must be, may coexist in the same aggregate, we shall see that they are fitted for entering into unlimited varieties of organic structures. The existence of such physiological units, peculiar to each species of organism, is not unaccounted for. They are evolved simultaneously with the evolution of the organisms they compose—they differentiate as fast as these organisms differentiate; and are made multitudinous in kind by the same actions which make the organism they compose multitudinous, in kind. This conception is clearly This is the conception which I have sought to convey, though it seems unsuccessfully, in the Principles of Biology; and which I have there used to interpret the many involved and mysterious It is, however, objected that "the living body in its development presents a long succession of differing forms; a continued series of changes for the whole length of which, according to Mr. Spencer's hypothesis, the physiological units must have an 'inherent tendency.' Could we more truly say of anything, 'it is unrepresentable in thought?'" I reply that if there is taken into account an element here overlooked, the process will not be found "unrepresentable in thought." This is the element of size or mass. To satisfy or balance the polarities of each order of physiological units, not only a certain structure of organism, but a certain size of organism is needed; for the complexities of that adult Possibly I have not succeeded by this explanation, any more than by the original explanation, in making this process "representable in thought." It is manifestly untrue, however, that I have, as alleged, re-introduced under a disguise the conception of a "vital principle." That I interpret embryonic development in terms of Matter and Motion, cannot, I think, be questioned. Whether the interpretation is adequate, must be a matter of opinion; but it is clearly a matter of fact, that I have not fallen into the inconsistency asserted by your reviewer. At the same time I willingly admit that, in the absence of certain statements which I have now supplied, he was not unwarranted in representing my conception in the way that he has done. NOTES Gross misrepresentations of this statement, which have been from time to time made, oblige me, much against my will, to add here an explanation of it. The last of these perversions, uttered in a lecture delivered at Belfast by the Rev. Professor Watts, D.D., is reported in the Belfast Witness of December 18, 1874; just while a third impression of this work is being printed from the plates. The report commences as follows:—"Dr. Watts, after showing that on his own confession Spencer was indebted for his facts to Huxley and Hooker, who," &c., &c. Wishing in this, as in other cases, to acknowledge indebtedness when conscious of it, I introduced the words referred to, in recognition of the fact that I had repeatedly questioned the distinguished specialists named, on matters beyond my knowledge, which were not dealt with in the books at my command. Forgetting the habits of antagonists, and especially theological antagonists, it never occurred to me that my expression of thanks to my friends for "information where my own was deficient," would be turned into the sweeping statement that I was indebted to them for my facts. Had Professor Watts looked at the preface to the second volume (the two having been published separately, as the prefaces imply), he would have seen a second expression of my indebtedness "for their valuable criticisms, and for the trouble they have taken in checking the numerous statements of fact on which the arguments proceed"—no further indebtedness being named. A moment's comparison of the two volumes in respect of their accumulations of facts, would have shown him what kind of warrant there was for his interpretation. Doubtless the Rev. Professor was prompted to make this assertion by the desire to discredit the work he was attacking; and having so good an end in view, thought it needless to be particular about the means. In the art of dealing with the language of opponents, Dr. Watts might give lessons to Monsignor Capel and Archbishop Manning. December 28th, 1874. In this passage as originally written (in 1862) they were described as incondensible; since, though reduced to the density of liquids, they had not been liquefied. Here and hereafter the word "atom" signifies a unit of something classed as an element, because thus far undecomposed by us. The word must not be supposed to mean that which its derivation implies. In all probability it is not a simple unit but a compound one. The name hydro-carbons was here used when these pages were written, thirty-four years ago. It was the name then current. In this case, as in multitudinous other cases, the substitution of newer words and phrases for older ones, is somewhat misleading. Putting the thoughts of 1862 in the language of 1897 gives an illusive impression of recency. It will perhaps seem strange to class oxygen as a crystalloid. But inasmuch as the crystalloids are distinguished from the colloids by their atomic simplicity, and inasmuch as sundry gases are reducible to a crystalline state, we are justified in so classing it. The remark made by a critic to the effect that in a mammal higher temperature diminishes the rate of molecular change in the tissues, leads me to add that the exhalation I have alleged is prevented if the heat rises above the range of variation normal to the organism; since, then, unusually rapid pulsations with consequent inefficient propulsion of the blood, cause a diminished rate of circulation. To produce the effect referred to in the text, heat must be associated with dryness; for otherwise evaporation is not aided. General evidence supporting the statement I have made is furnished by the fact that the hot and dry air of the eastern deserts is extremely invigorating; by the fact that all the energetic and conquering races of men have come from the hot and dry regions marked on the maps as rainless; and by the fact that travellers in Africa comment on the contrast between the inhabitants of the hot and dry regions (relatively elevated) and those of the hot and moist regions: active and inert respectively. The increase of respiration found to result from the presence of light, is probably an indirect effect. It is most likely due to the reception of more vivid impressions through the eyes, and to the consequent nervous stimulation. Bright light is associated in our experience with many of our greatest outdoor pleasures, and its presence partially arouses the consciousness of them, with the concomitant raised vital functions. To exclude confusion it may be well here to say that the word "atom" is, as before explained, used as the name for a unit of a substance at present undecomposed; while the word "molecule" is used as the name for a unit of a substance known to be compound. On now returning to the subject after many years, I meet with some evidence recently assigned, in a paper read before the Royal Society by Mr. J. W. Pickering, D.Sc. (detailing results harmonizing with those obtained by Prof. Grimaux), showing clearly how important an agent in vital actions is this production of isomeric changes by slight changes of conditions. Certain artificially produced substances, simulating proteids in other of their characters and reactions, were found to simulate them in coagulability by trifling disturbances. "In the presence of a trace of neutral salt they coagulate on heating at temperatures very similar to proteid solutions." And it is shown that by one of these factitious organic colloids a like effect is produced in coagulating the blood, to that "produced by the intravenous injection of a nucleoproteid." After this long interval during which other subjects have occupied me, I now find that the current view is similar to the view above set forth, in so far that a small molecular disturbance is supposed suddenly to initiate a great one, producing a change compared to an explosion. But while, of two proposed interpretations, one is that the fuse is nitrogenous and the charge a carbo-hydrate, the other is that both are nitrogenous. The relative probabilities of these alternative views will be considered in a subsequent chapter. When writing this passage I omitted to observe the verification yielded of the conclusion contained in §15 concerning the part played in the vital processes by the nitrogenous compounds. For these vegeto-alkalies, minute quantities of which produce such great effects in exalting the functions (e. g., a sixteenth of a grain of strychnia is a dose), are all nitrogenous bodies, and, by implication, relatively unstable bodies. The small amounts of molecular change which take place in these small quantities of the vegeto-alkalies when diffused through the system, initiate larger amounts of molecular change in the nitrogenous elements of the tissues. But the evidence furnished a generation ago by these vegeto-alkalies has been greatly reinforced by far more striking evidence furnished by other nitrogenous compounds—the various explosives. These, at the same time that they produce by their sudden decompositions violent effects outside the organism, also produce violent effects inside it: a hundredth of a grain of nitro-glycerine being a sufficient dose. Investigations made by Dr. J. B. Bradbury, and described by him in the Bradshaw Lecture on "Some New Vaso-Dilators" (see The Lancet, Nov. 16, 1895), details the effects of kindred bodies—methyl-nitrate, glycol-dinitrate, erythrol-tetranitrate. The first two, in common with nitro-glycerine, are stable only when cool and in the dark—sunlight or warmth decomposes them, and they explode by rapid heating or percussion. The fact which concerns us here is that the least stable—glycol-dinitrate—has the most powerful and rapid physiological effect, which is proportionately transient. In one minute the blood-pressure is reduced by one-fourth and in four minutes by nearly two-thirds: an effect which is dissipated in a quarter of an hour. So that this excessively unstable compound, decomposing in the body in a very short time, produces within that short time a vast amount of molecular change: acting, as it seems, not through the nervous system, but directly on the blood-vessels. This interpretation is said to be disproved by the fact that the carbo-hydrate contained in muscle amounts to only about 1.5 of the total solids. I do not see how this statement is to be reconciled with the statement cited three pages back from Professor Michael Foster, that the deposits of glycogen contained in the liver and in the muscles may be compared to the deposits in a central bank and branch banks. Before leaving the topic let me remark that the doctrine of metabolism is at present in its inchoate stage, and that the prevailing conclusions should be held tentatively. As showing this need an anomalous fact may be named. It was long held that gelatine is of small value as food, and though it is now recognized as valuable because serving the same purposes as fats and carbo-hydrates, it is still held to be valueless for structural purposes (save for some inactive tissue); and this estimate agrees with the fact that it is a relatively stable nitrogenous compound, and therefore unfit for those functions performed by unstable nitrogenous compounds in the muscular and other tissues. But if this is true, it seems a necessary implication that such substances as hair, wool, feathers, and all dermal growths chemically akin to gelatine, and even more stable, ought to be equally innutritive or more innutritive. In that case, however, what are we to say of the larva of the clothes-moth, which subsists exclusively on one or other of these substances, and out of it forms all those unstable nitrogenous compounds needful for carrying on its life and developing its tissues? Or again, how are we to understand the nutrition of the book-worm, which, in the time-stained leaves through which it burrows, finds no proteid save that contained in the dried-up size, which is a form of gelatine; or, once more, in what form is the requisite amount of nitrogenous substance obtained by the coleopterous larva which eats holes in wood a century old? This chapter and the following two chapters originally appeared in Part III of the original edition of the Principles of Psychology (1855): forming a preliminary which, though indispensable to the argument there developed, was somewhat parenthetical. Having now to deal with the general science of Biology before the more special one of Psychology, it becomes possible to transfer these chapters to their proper place. See Westminster Review for April, 1852.—Art. IV. "A Theory of Population." See Appendix A. This paragraph replaces a sentence that, in The Principles of Psychology, referred to a preceding chapter on "Method;" in which the mode of procedure here indicated was set forth as a mode to be systematically pursued in the choice of hypotheses. This chapter on Method is now included, along with other matter, in a volume entitled Various Fragments. Speaking of "the general idea of life" M. Comte says:—"Cette idÉe suppose, en effet, non-seulement celle d'un Être organisÉ de maniÈre À comporter l'État vital, mais aussi celle, non moins indispensable, d'un certain ensemble d'influences extÉrieures propres À son accomplissement. Une telle harmonie entre l'Être vivant et le milieu correspondant, caractÉrise evidemment la condition fondamentale de la vie." Commenting on de Blainville's definition of life, which he adopts, he says:—"Cette lumineuse dÉfinition ne me paraÎt laisser rien d'important À dÉsirer, si ce n'est une indication plus directe et plus explicite de ces deux conditions fondamentales co-relatives, nÉcessairement insÉparables de l'État vivant, un organisme dÉterminÉ et un milieu convenable." It is strange that M. Comte should have thus recognized the necessity of a harmony between an organism and its environment, as a condition essential to life, and should not have seen that the continuous maintenance of such inner actions as will counterbalance outer actions, constitutes life. [When the original edition was published Dr. J. H. Bridges wrote to me saying that in the Politique Positive, Comte had developed his conception further. On p. 413, denying "le prÉtendu antagonisme des corps vivants envers leurs milieux inorganiques," he says "au lieu de ce conflit, on a reconnu bientÔt que cette relation nÉcessaire constitue une condition fondamentale de la vie rÉelle, dont la notion systÉmatique consiste dans une intime conciliation permanente entre la spontanÉitÉ intÉrieure et la fatalitÉ extÉrieure." Still, this "conciliation permanente" seems to be a "condition" to life; not that varying adjustment of changes which life consists in maintaining. In presence of an ambiguity, the interpretation which agrees with his previous statement must be chosen.] In further elucidation of this general doctrine, see First Principles, §25. In ordinary speech Development is often used as synonymous with Growth. It hence seems needful to say that Development as here and hereafter used, means increase of structure and not increase of bulk. It may be added that the word Evolution, comprehending growth as well as Development, is to be reserved for occasions when both are implied. This paragraph originally formed part of a review-article on "Transcendental Physiology," published in 1857. When, in 1863, the preceding chapter was written, it had not occurred to me that there needed an accompanying chapter treating of Structure. The gap left by that oversight I now fill up. In doing this there have been included certain statements which are tacitly presupposed in the last chapter, and there may also be some which overlap statements in the next chapter. I have not thought it needful so to alter adjacent chapters as to remove these slight defects: the duplicated ideas will bear re-emphasizing. In connexion with this matter I add here a statement made by Prof. Foster which it is difficult to understand: "Indeed it has been observed that a dormouse actually gained in weight during a hybernating period; it discharged during this period neither urine nor fÆces, and the gain in weight was the excess of oxygen taken in over the carbonic acid given out." (Text-book of Physiology, 6th ed., Part II, page 859.) In the account of James Mitchell, a boy born blind and deaf, given by James Wardrop, F.R.S. (Edin. 1813), it is said that he acquired a "preternatural acuteness of touch and smell." The deaf Dr. Kitto described himself as having an extremely strong visual memory: he retained "a clear impression or image of everything at which he ever looked." Here, as in sundry places throughout this chapter, the necessities of the argument have obliged me to forestall myself, by assuming the conclusion reached in a subsequent chapter, that modifications of structure produced by modifications of function are transmitted to offspring. Whether the Volvox is to be classed as animal or vegetal is a matter of dispute; but its similarity to the blastula stage of many animals warrants the claim of the zoologists. While the proof was in my hands there was published in Science Progress an essay by Dr. T. G. Brodie on "The Phosphorus-containing Substances of the Cell." In this essay it is pointed out that "nucleic acid is particularly characterized by its instability.... In the process of purification it is extremely liable to decompose, with the result that it loses a considerable part of its phosphorus. In the second place it is most easily split up in another manner in which it loses a considerable part of its nitrogen.... To avoid the latter source of error he [Miescher] found that it was necessary to keep the temperature of all solutions down to 0°C., the whole time of the preparation." These facts tend strongly to verify the hypothesis that the nucleus is a source of perpetual molecular disturbance—not a regulating centre but a stimulating centre. The writing of the above section reminded me of certain allied views which I ventured to suggest nearly 50 years ago. They are contained in the Westminster Review for April, 1852, in an article entitled "A Theory of Population deduced from the General Law of Animal Fertility." It is there suggested that the "spermatozoon is essentially a neural element, and the ovum essentially a hÆmal element," or, as otherwise stated, that the "sperm-cell is co-ordinating matter and the germ-cell matter to be co-ordinated" (pp. 490-493). And along with this proposition there is given some chemical evidence tending to support it. Now if, in place of "neural" and "hÆmal," we say—the element that is most highly phosphorized and the element that is phosphorized in a much smaller degree; or if, in place of co-ordinating matter and matter to be co-ordinated, we say—the matter which initiates action and the matter which is made to act; there is disclosed a kinship between this early view and the view just set forth. In the last part of this work, "Laws of Multiplication," which is developed from the essay referred to, I left out the portion containing the quoted sentences, and the evidence supporting the conclusion drawn. Partly I omitted them because the speculation did not form an essential link in the general argument, and partly because I did not see how the suggested interpretation could hold of plants as well as of animals. If, however, the alleged greater staining capacity of the male generative nucleus in plants implies, as in other cases, that the male cell has a larger proportion of the phosphorized matter than the other elements concerned, then the difficulty disappears. As, along with the idea just named, the dropped portion of the original essay contains other ideas which seem to me worth preserving, I have thought it as well to reproduce it, in company with the chief part of the general argument as at first sketched out. It will be found in Appendix A to this volume. Unfortunately the word heterogenesis has been already used as a synonym for "spontaneous generation." Save by those few who believe in "spontaneous generation," however, little objection will be felt to using the word in a sense that seems much more appropriate. The meaning above given to it covers both Metagenesis and Parthenogenesis. Prof. Huxley avoids this difficulty by making every kind of Genesis a mode of development. His classification, which suggested the one given above, is as follows:—
The implication is that an essentially similar process occurs in those fragments of leaves used for artificial propagation. Besides the Begonias in general, I learn that various other plants are thus multiplied—Citron and orange trees, Hoya carnosa, Aucuba japonica, Clianthus puniceus, etc., etc. Bryophyllum calicinum, Rochea falcata, and Echeveria. I also learn that the following plants, among others, produce buds from their foliage leaves:—Cardamine pratensis, Nasturtium officinale, Roripa palustris, Brassica oleracea, Arabis pumila, Chelidonium majus, NymphÆa guianensis, Episcia bicolor, Chirita sivensis, Pinguicula Backeri, Allium, Gagea, Tolmia, Fritillaria, Ornithogalum, etc. In Cardamine and several others, a complete miniature plant is at once produced; in other cases bulbils or similar detachable buds. Among various examples I have observed, the most remarkable were among Foxgloves, growing in great numbers and of large size, in a wood between Whatstandwell Bridge and Crich, in Derbyshire. In one case the lowest flower on the stem contained, in place of a pistil, a shoot or spike of flower-buds, similar in structure to the embryo-buds of the main spike. I counted seventeen buds on it; of which the first had three stamens, but was otherwise normal; the second had three; the third, four; the fourth, four; &c. Another plant, having more varied monstrosities, evinced excess of nutrition with equal clearness. The following are the notes I took of its structure:—1st, or lowest flower on the stem, very large; calyx containing eight divisions, one partly transformed into a corolla, and another transformed into a small bud with bract (this bud consisted of a five-cleft calyx, four sessile anthers, a pistil, and a rudimentary corolla); the corolla of the main flower, which was complete, contained six stamens, three of them bearing anthers, two others being flattened and coloured, and one rudimentary; there was no pistil but, in place of it, a large bud, consisting of a three-cleft calyx of which two divisions were tinted at the ends, an imperfect corolla marked internally with the usual purple spots and hairs, three anthers sessile on this mal-formed corolla, a pistil, a seed vessel with ovules, and, growing to it, another bud of which the structure was indistinct. 2nd flower, large; calyx of seven divisions, one being transformed into a bud with bract, but much smaller than the other; corolla large but cleft along the top; six stamens with anthers, pistil, and seed-vessel. 3rd flower, large; six-cleft calyx, cleft corolla, with six stamens, pistil, and seed-vessel, with a second pistil half unfolded at its apex. 4th flower, large; divided along the top, six stamens. 5th flower, large; corolla divided into three parts, six stamens. 6th flower, large; corolla cleft, calyx six cleft, the rest of the flower normal. 7th, and all succeeding flowers, normal. While this chapter is under revision, another noteworthy illustration has been furnished to me by a wall-trained pear tree which was covered in the spring by luxuriant "foreright" shoots. As I learned from the gardener, it was pruned just as the fruit was setting. A large excess of sap was thus thrown into other branches, with the result that in a number of them the young pears were made monstrous by reversion. In some cases, instead of the dried up sepals at the top of the pear, there were produced good sized leaves; and in other cases the seed-bearing core of the pear was transformed into a growth which protruded through the top of the pear in the shape of a new shoot. In partial verification, Mr. Tansley writes:—"Prof. Klebs of Basel has shown that in Hydrodictyon, gametes can only be produced by the cells of a net when these are above a certain size and age; and then only under conditions unfavourable to growth, such as a feeble light or poverty of nutritive inorganic salts or absence of oxygen, or a low temperature in the water containing the plant. The presence of organic substances, especially sugar, also acts as a stimulus to the formation of gametes, and this is also the case in Vaucheria. Many other AlgÆ produce gametes mainly at the end of the vegetative season, when food is certainly difficult to obtain in their natural habitat, and we may well suppose that their assimilative power is waning. Where, however, as is the case in Vaucheria, the plant depends for propagation mainly on the production of fertilized eggs, we find the sexual organs often produced in conditions very favourable to vegetative growth, in opposition to those cases such as Hydrodictyon, where the chief means of propagation is by zoospores. So that side by side with, and to some extent obscuring, the principle developed above we have a clear adaptation of the production of reproductive cells to the special circumstances of the case." This establishment by survival of the fittest of reproductive processes adapted to variable conditions, is indirectly elucidated by the habits of salmon. As salmon thrive in the sea and fall out of condition in fresh water (having during their sea-life not exercised the art of catching fresh-water prey), the implication is that the species would profit if all individuals ran up the rivers just before spawning time in November. Why then do most of them run up during many preceding months? Contemplation of the difficulties which lie in the way to the spawning grounds, will, I think, suggest an explanation. There are falls to be leaped and shallow rapids to be ascended. These obstacles cannot be surmounted when the river is low. A fish which starts early in the season has more chances of getting up the falls and the rapids than one which starts later; and, out of condition as it will be, may spawn, though not well. On the other hand, one which starts in October, if floods occur appropriately, may reach the upper waters and then spawn to great advantage; but in the absence of adequate rains it may fail altogether to reach the spawning grounds. Hence the species profits by an irregularity of habits adapted to meet irregular contingencies. I owe to Mr. (now Sir John) Lubbock an important confirmation of this view. After stating his belief that between Crustaceans and Insects there exists a physiological relation analogous to that which exists between water vertebrata and land-vertebrata, he pointed out to me that while among Insects there is a definite limit of growth, and an accompanying definite commencement of reproduction, among Crustaceans, where growth has no definite limit, there is no definite relation between the commencement of reproduction and the decrease or arrest of growth. While this chapter is passing through the press, I learn from Mr. White Cooper, that not only are near sight, long sight, dull sight, and squinting, hereditary; but that a peculiarity of vision confined to one eye is frequently transmitted: re-appearing in the same eye in offspring. An instance here occurs of the way in which those who are averse to a conclusion will assign the most flimsy reasons for rejecting it. Rather than admit that the eyes of these creatures living in darkness have disappeared from lack of use, some contend that such creatures would be liable to have their eyes injured by collisions with objects, and that therefore natural selection would favour those individuals in which the eyes had somewhat diminished and were least liable to injury: the implication being that the immunity from the inflammations due to injuries would be so important a factor in life as to cause survival. And this is argued in presence of the fact that one of the most conspicuous among these blind cave-animals is a cray-fish, and that the cray-fish in its natural habitat is in the habit of burrowing in the banks of rivers holes a foot or more deep, and has its eyes exposed to all those possible blows and frictions which the burrowing involves! In addition to the numerous illustrations given by Mr. Sedgwick, here is one which Colonel A. T. Fraser published in Nature for Nov. 9, 1893, concerning two Hindoo dwarfs:—"In speech and intelligence the dwarfs were indistinguishable from ordinary natives of India. From an interrogation of one of them, it appeared that he belonged to a family all the male members of which have been dwarfs for several generations. They marry ordinary native girls, and the female children grow up like those of other people. The males, however, though they develop at the normal rate until they reach the age of six, then cease to grow, and become dwarfs." This remarkable case appears to militate against the conclusion, drawn a few pages back, that the increase of a peculiarity by coincidence of "spontaneous variations" in successive generations, is very improbable; and that the special superiorities of musical composers cannot have thus arisen. The reply is that the extreme frequency of the occurrence among so narrow a class as that of musical composers, forbids the interpretation thus suggested. I omitted to name here a cause which may be still more potent in producing irregularity in the results of cousin-marriages. So far as I can learn, no attempt has been made to distinguish between such results as arise when the related parents from whom the cousins descend are of the same sex and those which arise when they are of different sexes. In the one case two sisters have children who intermarry; and in the other case a brother and a sister have children who intermarry. The marriages of cousins in these two cases may be quite dissimilar in their results. If there is a tendency to limitation of heredity by sex—if daughters usually inherit more from the mother than sons do, while sons inherit more from the father than from the mother, then two sisters will on the average of cases be more alike in constitution than a sister and a brother. Consequently the descendants of two sisters will differ less in their constitutions than the descendants of a brother and a sister; and marriage in the first case will be more likely to prove injurious from absence of dissimilarity in the physiological units than marriage in the second. My own small circle of friends furnishes evidence tending to verify this conclusion. In one instance two cousins who intermarried are children of two sisters, and they have no offspring. In another the cousins who intermarried are children of two brothers, and they have no offspring. In the third case the cousins were descendants of two brothers and only one child resulted. A propos of this sentence one of my critics writes:—"I cannot find in this book the statement as first made that the 'life of an individual is maintained by the unequal and ever-varying actions of incident forces on its different parts.' Recent physiological work offers a startling example of the statement." To the question contained in the first sentence the answer is that I have not made the statement in the above words, but that it is implied in the chapter entitled "The Degree of Life varies as the Degree of Correspondence," and more especially in §36, which, towards its close, definitely involves the statement. The verifying evidence my critic gives me is this:— "Prof. Sherrington has shown that if the sensory roots of the spinal nerves are cut one by one there is at first no general effect produced. That is to say, the remainder of the nervous system continues to function as before. This condition (lack of general effect) persists until about six pairs have been cut. With the severance of the seventh pair, however, the whole central nervous system ceases to function, so that stimulation of intact sensory nerves produces no reflex action. After a variable period, but one of many hours duration, the power of functioning is recovered. That is to say, if the sensory impulses (from the skin, &c.) reaching the central nervous system are rapidly reduced in amount, there comes a point where those remaining do not suffice to keep the structure 'awake.' After a time, however, it adjusts itself to work with the diminished supply. Similarly Strumpell describes the case of a boy 'whose sensory inlets were all paralyzed except one eye and one ear.' When these were closed he instantly fell asleep." Fifty years before the discovery of the RÖntgen rays and those habitually emanating from uranium, it had been observed by Moser that under certain conditions the surfaces of metals receive permanent impressions from appropriate objects placed upon them. Such facts show that the molecules of substances propagate in all directions special ethereal undulations determined by their special constitutions. This classification, and the three which follow it, I quote (abridging some of them) from Prof. Agassiz's "Essay on Classification." For explanations, see "Illogical Geology," Essays, Vol. I. How much we may be misled by assuming that because the remains of creatures of high types have not been found in early strata, such creatures did not exist when those strata were formed, has recently (1897) been shown by the discovery of a fossil Sea-cow in the lower Miocene of Hesse-Darmstadt. The skeleton of this creature proves that it differed from such Sirenian mammals as the existing Manatee only in very small particulars: further dwindling of disused parts being an evident cause. The same is true as regards, now, we consider that since the beginning of Miocene days this aberrant type of mammal has not much increased its divergence from the ordinary mammalian type; if we then consider how long it must have taken for this large aquatic mammal (some eight or ten feet long) to be derived by modification from a land-mammal; and if then we contemplate the probable length of the period required for the evolution of that land-mammal out of a pre-mammalian type; we seem carried back in thought to a time preceding any of our geologic records. We are shown that the process of organic evolution has most likely been far slower than is commonly supposed. Since this passage was written, in 1863, there has come to light much more striking evidence of change from a more generalized to a less generalized type during geologic time. In a lecture delivered by him in 1876, Prof. Huxley gave an account of the successive modifications of skeletal structure in animals allied to the horse. Beginning with the Orohippus of the Eocene formation, which had four complete toes on the front limb and three toes on the hind limb, he pointed out the successive steps by which in the Mesohippus, Miohippus, Protohippus, and Pliohippus, there was a gradual approach to the existing horse. Several of the arguments used in this chapter and in that which follows it, formed parts of an essay on "The Development Hypothesis," originally published in 1852. Studies from the Morphological Laboratory in the University of Cambridge, vol. vi, p. 84. Ibid., p. 81. Studies from the Morphological Laboratory in the University of Cambridge, vol. vi, p. 89. Early in our friendship (about 1855) Prof. Huxley expressed to me his conviction that all the higher articulate animals have twenty segments or somites. That he adhered to this view in 1880, when his work on The Crayfish was published, is shown by his analysis there given of the twenty segments existing in this fluviatile crustacean; and adhesion to it had been previously shown in 1877, when his work on The Anatomy of Invertebrated Animals was published. On p. 398 of that work he writes:—"In the abdomen there are, at most, eleven somites, none of which, in the adult, bear ambulatory limbs. Thus, assuming the existence of six somites in the head, the normal number of somites in the body of insects will be twenty, as in the higher Crustacea and Arachnida." To this passage, however, he puts the note:—"It is open to question whether the podical plates represent a somite; and therefore it must be recollected that the total number of somites, the existence of which can be actually demonstrated in insects, is only seventeen, viz., four for the head, three for the thorax, and ten for the abdomen." I have changed the number twenty, which in the original edition occurred in the text, to the number seventeen in deference to suggestions made to me; though I find in Dr. Sharp's careful and elaborate work on the Insecta, that Viallanes and Cholodkovsky agree with Huxley in believing that there are six somites in the insect-head. The existence of a doubt on this point, however, does not essentially affect the argument, since there is agreement among morphologists respecting the constancy of the total number of somites in insects. To avoid circumlocution I let these words stand, though they are not truly descriptive; for the prosperity of imported species is largely, if not mainly, caused by the absence of those natural enemies which kept them down at home. While these pages are passing through the press (in 1864), Dr. Hooker has obliged me by pointing out that "plants afford many excellent examples" of analogous transitions. He says that among true "water plants," there are found, in the same species, varieties which have some leaves submerged and some floating; other varieties in which they are all floating; and other varieties in which they are all submerged. Further, that many plants characterized by floating leaves, and which have all their leaves floating when they grow in deeper water, are found with partly aerial leaves when they grow in shallower water; and that elsewhere they occur in almost dry soil with all their leaves aerial. It will be seen that the argument naturally leads up to this expression—Survival of the Fittest—which was here used for the first time. Two years later (July, 1866) Mr. A. R. Wallace wrote to Mr. Darwin contending that it should be substituted for the expression "Natural Selection." Mr. Darwin demurred to this proposal. Among reasons for retaining his own expression he said that I had myself, in many cases, preferred it—"continually using the words Natural Selection." (Life and Letters, &c., vol. III, pp. 45-6.) Mr. Darwin was quite right in his statement, but not right in the motive he ascribed to me. My reason for frequently using the phrase "Natural Selection," after the date at which the phrase "Survival of the Fittest" was first used above, was that disuse of Mr. Darwin's phrase would have seemed like an endeavour to keep out of sight my own indebtedness to him, and the indebtedness of the world at large. The implied feeling has led me ever since to use the expressions Natural Selection and Survival of the Fittest with something like equal frequency. I am indebted to Mr. [now Sir W.] Flower for the opportunity of examining the many skulls in the Museum of the College of Surgeons for verification of this. Unfortunately the absence, in most cases, of some or many teeth, prevented me from arriving at that specific result which would have been given by weighing a number of the under jaws in each race. Simple inspection, however, disclosed a sufficiently-conspicuous difference. The under jaws of Australians and Negroes, when collated with those of Englishmen, were visibly larger, not only relatively but absolutely. One Australian jaw only seemed about of the same size as an average English jaw; and this (probably the jaw of a woman), belonging as it did to a smaller skull, bore a greater ratio to the whole body of which it formed part, than did an English jaw of the same actual size. In all the other cases, the under jaws of these inferior races (containing larger teeth than our own) were absolutely more massive than our own—often exceeding them in all dimensions; and relatively to their smaller skeletons were much more massive. Let me add that the Australian and Negro jaws are thus strongly contrasted, not with all British jaws, but only with the jaws of the civilized British. An ancient British skull in the collection possesses a jaw almost or quite as massive as those of the Australian skulls. All this is in harmony with the alleged relation between greater size of jaws and greater action of jaws, involved by the habits of savages. [In 1891 Mr. F. Howard Collins carefully investigated this matter: measuring ten Australian, ten Ancient British, and ten recent English skulls in the College of Surgeons Museum. The result proved an absolute difference of the kind above indicated, and a far greater relative difference. To ascertain this last a common standard of comparison was established—an equal size of skull in all the cases; and then when the relative masses or cubic sizes of the jaws were calculated, the result which came out was this:—Australian jaw, 1948; Ancient British jaw, 1135; Recent English jaw, 1030. "Hence," in the words of Mr. Collins, "the mass of the Recent English jaw is, roughly speaking, half that of the Australian relatively to that of the skull, and a ninth less than that of the Ancient British." He adds verifying evidence from witnesses who have no hypothesis to support—members of the Odontological Society. The Vice-President, Mr. Mummery, remarks of the Australians that "the jaw-bones are powerfully developed, and large in proportion to the cranium."] As bearing on the question of the varieties of Man, let me here refer to a paper on "The Origin of the Human Races" read before the Anthropological Society, March 1st, 1864, by Mr. Alfred Wallace. In this paper, Mr. Wallace shows that along with the attainment of that intelligence implied by the use of implements, clothing, &c., there arises a tendency for modifications of brain to take the place of modifications of body: still, however, regarding the natural selection of spontaneous variations as the cause of the modifications. But if the foregoing arguments be valid, natural selection here plays but the secondary part of furthering the adaptations otherwise caused. It is true that, as Mr. Wallace argues, and as I have myself briefly indicated (see Westminster Review, for April, 1852, pp. 496-501), the natural selection of races leads to the survival of the more cerebrally-developed, while the less cerebrally-developed disappear. But though natural selection acts freely in the struggle of one society with another; yet, among the units of each society, its action is so interfered with that there remains no adequate cause for the acquirement of mental superiority by one race over another, except the inheritance of functionally-produced modifications. Darwin and after Darwin, Part II, p. 99. Essays upon Heredity, vol. i, p. 90. In a letter published by Dr. Romanes in Nature, for April 26, 1894, he alleges three reasons why "as soon as selection is withdrawn from an organ the minus variations of that organ outnumber the plus variations." The first is that "the survival-mean must descend to the birth-mean." The interpretation of this is that if the members of a species are on the average born with an organ of the required size, and if they are exposed to natural selection, then those in which the organ is relatively small will some of them die, and consequently the mean size of the organ at adult age will be greater than at birth. Contrariwise, if the organ becomes useless and natural selection does not operate on it, this difference between the birth-mean and the survival-mean disappears. Now here, again, the plus variations and their effects are ignored. Supposing the organ to be useful, it is tacitly assumed that while minus variations are injurious, plus variations are not injurious. This is untrue. Superfluous size of an organ implies several evils:—Its original cost is greater than requisite, and other organs suffer; the continuous cost of its nutrition is unduly great, involving further injury; it adds needlessly to the weight carried and so again is detrimental; and there is in some cases yet a further mischief—it is in the way. Clearly, then, those in which plus variations of the organ have occurred are likely to be killed off as well as those in which minus variations have occurred; and hence there is no proof that the survival-mean will exceed the birth-mean. Moreover the assumption has a fatal implication. To say that the survival-mean of an organ is greater than the birth-mean is to say that the organ is greater in proportion to other organs than it was at birth. What happens if instead of one organ we consider all the organs? If the survival-mean of a particular organ is greater than its birth-mean, the survival mean of each other organ must also be greater. Thus the proposition is that every organ has become larger in relation to every other organ!—a marvellous proposition. I need only add that Dr. Romanes' inferences with respect to the two other causes—atavism and failing heredity—are similarly vitiated by ignoring the plus variations and their effects. Westminster Review, January, 1860. See also Essays, &c., vol. i, p. 290. "On Orthogenesis and the Impotence of Natural Selection in Species-Formation," pp. 2, 19, 22, 24. Address to Plymouth Institution, at opening of Session 1895-6. Westminster Review, April, 1857. "Progress: its Law and Cause." See also Essays, vol. i. It may be needful to remark, that by the proposed expression it is intended to define—not Life in its essence; but, Life as manifested to us—not Life as a noumenon: but, Life as a phenomenon. The ultimate mystery is as great as ever: seeing that there remains unsolved the question—What determines the co-ordination of actions? Prin. of Phys., 2nd edit., p. 77. Ibid., 3rd edit., p 249. Ibid., p. 124. Agassiz and Gould, p. 274. Prin. of Phys., 3rd edit., p. 964. "Parthenogenesis," p. 8. Prin. of Phys., p. 92. Ibid., p. 93. Ibid., p. 917. "A General Outline of the Animal Kingdom." By Prof. T. R. Jones, F. G. S., p. 61. Carpenter. Prin. of Phys., p. 873. Ibid., p. 203. Ibid., p. 209. Ibid., p. 249. Ibid., p. 249. Ibid., p. 250. Prin. of Phys., p. 256. Ibid., p. 212. Ibid., p. 266. Prin. of. Phys., p. 267. Ibid., p. 276. Ibid., 2nd edit., p. 115. Prin. of Phys., p. 954. Ibid., p. 958. Ibid., p. 688. Ibid., p. 958. "A General Outline of the Animal Kingdom." By Professor T. R. Jones, p. 61. Prin. of Phys., p. 907. Should it be objected that in the higher plants the sperm-cell and germ-cell differ, though no distinct co-ordinating system exists, it is replied that there is co-ordination of actions, though of a feeble kind, and that there must be some agency by which this is carried on. It is a significant fact that amongst the dioecious invertebrata, where the nutritive system greatly exceeds the other systems in development, the female is commonly the largest, and often greatly so. In some of the Rotifera the male has no nutritive system at all. See Prin. of Phys., p. 954. Prin. of Phys., p. 908. "Parthenogenesis," pp. 66, 67. "Lectures on Animal Chemistry." By Dr. Bence Jones. Medical Times, Sept. 13th, 1851. See also Prin. of Phys., p. 171. CyclopÆdia of Anatomy and Physiology, Vol. IV, p. 506. From a remark of Drs. Wagner and Leuckart this chemical evidence seems to have already suggested the idea that the sperm-cell becomes "metamorphosed into the central parts of the nervous system." But though they reject this assumption, and though the experiments of Mr. Newport clearly render it untenable, yet none of the facts latterly brought to light conflict with the hypothesis that the sperm-cell contains unorganized co-ordinating matter. Quain's Elements of Anatomy, p. 672. The maximum weight of the horse's brain is 1 lb. 7 ozs.; the human brain weighs 3 lbs., and occasionally as much as 4 lbs.; the brain of a whale, 75 feet long, weighed 5 lbs. 5 ozs.; and the elephant's brain reaches from 8 lbs. to 10 lbs. Of the whale's fertility we know nothing; but the elephant's quite agrees with the hypothesis. The elephant does not attain its full size until it is thirty years old, from which we may infer that it arrives at a reproductive age later than man does; its period of gestation is two years, and it produces one at a birth. Evidently, therefore, it is much less prolific than man. See MÜller's Physiology (Baly's translation), p. 815, and Quain's Elements of Anatomy, p. 671. That the size of the nervous system is the measure of the ability to maintain life, is a proposition that must, however, be taken with some qualifications. The ratio between the amounts of gray and white matter present in each case is probably a circumstance of moment. Moreover, the temperature of the blood may have a modifying influence; seeing that small nervous centres exposed to rapid oxidation will be equivalent to larger ones more slowly oxidized. Indeed, we see amongst mankind, that though, in the main, size of brain determines mental power, yet temperament exercises some control. There is reason to think, too, that certain kinds of nervous action involve greater consumption of nervous tissue than others; and this will somewhat complicate the comparisons. Nevertheless, these admissions do not affect the generalization as a whole, but merely prepare us to meet with minor irregularities. Let me here note in passing a highly significant implication. The development of nervous structures which in such cases take place, cannot be limited to the finger-ends. If we figure to ourselves the separate sensitive areas which severally yield independent feelings, as constituting a network (not, indeed, a network sharply marked out, but probably one such that the ultimate fibrils in each area intrude more or less into adjacent areas, so that the separations are indefinite), it is manifest that when, with exercise, the structure has become further elaborated, and the meshes of the network smaller, there must be a multiplication of fibres communicating with the central nervous system. If two adjacent areas were supplied by branches of one fibre, the touching of either would yield to consciousness the same sensation: there could be no discrimination between points touching the two. That there may be discrimination, there must be a distinct connection between each area and the tract of grey matter which receives the impressions. Nay more, there must be, in this central recipient-tract, an added number of the separate elements which, by their excitements, yield separate feelings. So that this increased power of tactual discrimination implies a peripheral development, a multiplication of fibres in the trunk-nerve, and a complication of the nerve-centre. It can scarcely be doubted that analogous changes occur under analogous conditions throughout all parts of the nervous system—not in its sensory appliances only, but in all its higher co-ordinating appliances, up to the highest. Essays upon Heredity, p. 87. Les Maladies des Vers À soie, par L. Pasteur, Vol. I, p. 39. Curiously enough, Weismann refers to, and recognizes, syphilitic infection of the reproductive cells. Dealing with Brown-SÉquard's cases of inherited epilepsy (concerning which, let me say, that I do not commit myself to any derived conclusions), he says:—"In the case of epilepsy, at any rate, it is easy to imagine [many of Weismann's arguments are based on things 'it is easy to imagine'] that the passage of some specific organism through the reproductive cells may take place, as in the case of syphilis" (p. 82). Here is a sample of his reasoning. It is well known that epilepsy is frequently caused by some peripheral irritation (even by the lodging of a small foreign body under the skin), and that, among peripheral irritations causing it, imperfect healing is one. Yet though, in Brown-SÉquard's cases, a peripheral irritation caused in the parent by local injury was the apparent origin, Weismann chooses gratuitously to assume that the progeny were infected by "some specific organism," which produced the epilepsy! And then though the epileptic virus, like the syphilitic virus, makes itself at home in the egg, the parental protoplasm is not admitted! Philosophical Transactions of the Royal Society for the Year 1821, Part I, pp. 20-24. It will, I suppose, be said that the non-inheritance of mutilations constitutes evidence of the kind here asked for. The first reply is that the evidence is conflicting, as it may well be. It is forgotten that to have valid evidence of non-inheritance of mutilations, it is requisite that both parents shall have undergone mutilation, and that this does not often happen. If they have not, then, assuming the inheritableness of mutilations, there would, leaving out other causes, be an equal tendency to appearance and non-appearance of the mutilation in offspring. But there is another cause—the tendency to reversion, which ever works in the direction of cancelling individual characters by the return to ancestral characters. So that even were the inheritance of mutilations to be expected (and for myself I may say that its occurrence surprises me), it could not be reasonably looked for as more than exceptional: there are two strong countervailing tendencies. But now, in the second place, let it be remarked that the inheritance or non-inheritance of mutilations is beside the question. The question is whether modifications of parts produced by modifications of functions are inheritable or not. And then, by way of disproof of their inheritableness, we are referred to cases in which the modifications of parts are not produced by modifications of functions, but are otherwise produced! See First Principles, Part II, Chap. XXII, "Equilibration." Principles of Biology, §46, (No. 8. April, 1863). Ibid. This must not be understood as implying that while the mass increases as the cubes, the quantity of motion which can be generated increases only as the squares; for this would not be true. The quantity of motion is obviously measured, not by the sectional areas of the muscles alone, but by these multiplied into their lengths, and therefore increases as the cubes. But this admission leaves untouched the conclusion that the ability to bear stress increases only as the squares; and thus limits the ability to generate motion, by relative incoherence of materials. The Transactions of the LinnÆan Society of London, Vol. XXII, p. 215. The estimate of Reaumur, cited by Kirby and Spence, is still higher—"in five generations one Aphis may be the progenitor of 5,904,900,000 descendants; and that it is supposed that in one year there may be twenty generations." (Introduction to Entomology, Vol. I, p. 175) A Manual of the Anatomy of Invertebrated Animals, by T. H. Huxley, p. 206. Respecting the Eloidea I learn that in 1879—thirty years after it had become a pest—one solitary male plant was found in a pond near Edinburgh; but "in an exhaustive inquiry on the plant made by Dr. Groenland, of Copenhagen, he could find no trace of any male specimens having been found in Europe other than the Scotch." In waters from which the Eloidea has disappeared, it seems to have done so in consequence of the growth of an Alga, which has produced turbid water unfavourable to it. That is to say, the decreased multiplication of somatic cells in some cases, is not due to any exhaustion, but is caused by the rise of enemies or adverse conditions; as happens generally with introduced species of plants and animals which multiply at first enormously, and then, without any loss of reproductive power, begin to decrease under the antagonizing influences which grow up. A Text Book of Human Physiology. By Austin Flint, M.D., LL.D. Fourth edition. New York: D. Appleton & Co. 1888. Page 797. This supposition I find verified by Mr. A. S. Packard in his elaborate monograph on "The Cave Fauna of North America, &c.," as also in his article published in the American Naturalist, September, 1888; for he there mentions "variations in Pseudotremia cavernarum and Tomocerus plumbeus, found living near the entrance to caves in partial daylight." The facts, as accumulated by Mr. Packard, furnished a much more complete answer to Prof. Lankester than is above given, as, for example, the "blindness of Neotoma, or the Wood-Rat of Mammoth Cave." It seems that there are also "cave beetles, with or without rudimentary eyes," and "eyeless spiders" and Myriapods. And there are insects, as some "species of Anophthalmus and Adelops, whose larvÆ are lacking in all traces of eyes and optic nerves and lobes." These instances cannot be explained as sequences of an inrush of water carrying with it the remote ancestors, some of which did not find their way out; nor can others of them be explained by supposing an inrush of air, which did the like. See "Social Organism" in Westminster Review for January, 1860; also Principles of Sociology, §247. Contemporary Review, September, 1893. Evolution of Sex, p. 50. Souvenirs Entomologiques, 3me SÉrie, p. 328. Natural History of Bees, new ed., p. 33. Origin of Species, 6th ed., p. 232. Contemporary Review, September, 1893, p. 333. The Entomologist's Monthly Magazine, March, 1892, p. 61. Perhaps it will be alleged that nerve-matter is costly, and that this minute economy might be of importance. Anyone who thinks this will no longer think it after contemplating a litter of half-a-dozen young rabbits (in the wild rabbit the number varies from four to eight); and on remembering that the nerve-matter contained in their brains and spinal cords, as well as the materials for building up the bones, muscles, and viscera of their bodies, has been supplied by the doe in the space of a month; at the same time that she has sustained herself and carried on her activities: all this being done on relatively poor food. Nerve-matter cannot be so very costly then. Loc. cit., p. 318. The Germ Plasm, p. 54. While Professor Weismann has not dealt with my argument derived from the distribution of discriminativeness on the skin, it has been criticized by Mr. McKeen Cattell, in the last number of Mind (October, 1893). His general argument, vitiated by extreme misconceptions, I need not deal with. He says:—"Whether changes acquired by the individual are hereditary, and if so to what extent, is a question of great interest for ethics no less than for biology. But Mr. Spencer's application of this doctrine to account for the origin of species [!] simply begs the question. He assumes useful variations [!]—whether of structure or habit is immaterial—without attempting to explain their origin": two absolute misstatements in two sentences! The only part of Mr. Cattell's criticism requiring reply is that which concerns the "sensation-areas" on the skin. He implies that since Weber, experimental psychologists have practically set aside the theory of sensation areas: showing, among other things, that relatively great accuracy of discrimination can be quickly acquired by "increased interest and attention.... Practice for a few minutes will double the accuracy of discrimination, and practice on one side of the body is carried over to the other." To me it seems manifest that "increased interest and attention" will not enable a patient to discriminate two points where a few minutes before he could perceive only one. That which he can really do in this short time is to learn to discriminate between the massiveness of a sensation produced by two points and the massiveness of that produced by one, and to infer one point or two points accordingly. Respecting the existence of sensation-areas marked off from one another, I may, in the first place, remark that since the eye originates as a dermal sac, and since its retina is a highly developed part of the sensitive surface at large, and since the discriminative power of the retina depends on the division of it into numerous rods and cones, each of which gives a separate sensation-area, it would be strange were the discriminative power of the skin at large achieved by mechanism fundamentally different. In the second place I may remark that if Mr. Cattell will refer to Professor Gustav Retzius's Biologische Untersuchungen, New Series, vol. iv (Stockholm, 1892), he will see elaborate diagrams of superficial nerve-endings in various animals showing many degrees of separateness. I guarded myself against being supposed to think that the sensation-areas are sharply marked off from one another; and suggested, contrariwise, that probably the branching nerve-terminations intruded among the branches of adjacent nerve-terminations. Here let me add that the intrusion may vary greatly in extent; and that where the intruding fibres run far among those of adjacent areas, the discriminativeness will be but small, while it will be great in proportion as each set of branching fibres is restricted more nearly to its own area. All the facts are explicable on this supposition. To save space and exclude needless complication I have omitted these passages from the preceding divisions of this appendix. Though Professor Weismann does not take up the challenge, Dr. Romanes does. He says:—"When selection is withdrawn there will be no excessive plus variations, because so long as selection was present the efficiency of the organ was maintained at its highest level: it was only the minus variations which were then eliminated" (Contemporary Review, p. 611). In the first place, it seems to me that the phrases used in this sentence beg the question. It says that "the efficiency of the organ was maintained at its highest level"; which implies that the highest level (tacitly identified with the greatest size) is the best and that the tendency is to fall below it. This is the very thing I ask proof of. Suppose I invert the idea and say that the organ is maintained at its right size by natural selection, because this prevents increase beyond the size which is best for the organism. Every organ should be in due proportion, and the welfare of the creature as a whole is interfered with by excess as well as by defect. It may be directly interfered with—as for instance by too big an eyelid; and it may be indirectly interfered with, where the organ is large, by needless weight and cost of nutrition. In the second place the question which here concerns us is not what natural selection will do with variations. We are concerned with the previous question—What variations will arise? An organ varies in all ways; and, unless reason to the contrary is shown, the assumption must be that variations in the direction of increase are as frequent and as great as those in the direction of decrease. Take the case of the tongue. Certainly there are tongues inconveniently large, and probably tongues inconveniently small. What reason have we for assuming that the inconveniently small tongues occur more frequently than the inconveniently large ones? None that I can see. Dr. Romanes has not shown that when natural selection ceases to act on an organ the minus variations in each new generation will exceed the plus variations. But if they are equal the alleged process of panmixia has no place. The Variation of Animals and Plants under Domestication, vol. ii, p. 292. Journal of the Anthropological Institute for 1885, p. 253. In "The All-Sufficiency of Natural Selection" (Contemporary Review, Sept., 1893, p. 311), Professor Weismann writes:—"I have ever contended that the acceptance of a principle of explanation is justified, if it can be shown that without it certain facts are inexplicable." Unless, then, Prof. Weismann can show that the distribution of discriminativeness is otherwise explicable, he is bound to accept the explanation I have given, and admit the inheritance of acquired characters. Prof. Weismann is unaware that the view here ascribed to Roux, writing in 1881, is of far earlier date. In the Westminster Review for January, 1860, in an essay on "The Social Organism," I wrote:—"One more parallelism to be here noted, is that the different parts of a social organism, like the different parts of an individual organism, compete for nutriment; and severally obtain more or less of it according as they are discharging more or less duty." (See also Essays, i, 290.) And then, in 1876, in The Principles of Sociology, vol. i, §247, I amplified the statement thus:—"All other organs, therefore, jointly and individually, compete for blood with each organ ... local tissue-formation (which under normal conditions measures the waste of tissue in discharging function) is itself a cause of increased supply of materials ... the resulting competition, not between units simply, but between organs, causes in a society, as in a living body, high nutrition and growth of parts called into greatest activity by the requirements of the rest." Though I did not use the imposing phrase "intra-individual-selection," the process described is the same. Proceedings of the Biological Society of Washington, vol. ix. Romanes Lecture, p. 29. Ibid., p. 35. This interpretation harmonizes with a fact which I learn from Prof. Riley, that there are gradations in this development, and that in some species the ordinary neuters swell their abdomens so greatly with food that they can hardly get home. |
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