DO SNAKES INCUBATE THEIR EGGS?

WE come now to treat of facts no less interesting than surprising in ophidian biographies. Already we have recounted almost marvellous powers possessed by this class of animals—functions which are volitionary, such as the management of their trachea, the voluntary folding back or unfolding of certain teeth, the practical adaptation of their ribs and coils to what we may almost call manual work, and now, most astonishing of all, the voluntary deposition or retention of ova, even of young.

‘Snakes are either oviparous or viviparous,’ is what we are accustomed to read, followed by the explanation that the former are those which lay eggs, and the latter those which produce their young alive. To these two chief distinctions, the more recent one of ovoviviparous has been added, to describe some intermediate cases where the egg is ruptured in parturition, so that again a fully-formed young one is born. For broad distinctions the three terms do well enough, though many exceptions exist. The grand distinction of ‘viper’ as applied to those snakes which produce live young, was adopted when snakes were first observed and described by classic writers.

‘Vipers alone are viviparous,’ wrote Aristotle. ‘Sometimes the little vipers eat through their mother and come forth. The viper brings forth one at a time in one day, but she brings forth more than twenty little vipers. Other serpents produce their eggs externally, and these eggs are connected with each other like the necklaces of women. But when they bring forth, they deposit their eggs in the earth, and there incubate them. These eggs they disclose the following year.’ We do not quote the above as all fact, but rather to show how very much there has been to unlearn since Aristotle was accepted as an authority. The shadow of truth and the mention of a possible fact as an invariable rule are dangerous mistakes, for, as we have already shown, where a snake is concerned, one can rarely feel safe in asserting anything as positive. It is not impossible that, owing to disease or accident, some gravid viper may have been so wounded as to enable her young to make their dÉbut through her ruptured side. Such an occurrence has been seen in our own time. Aristotle or his authority may even have witnessed such an accident, and recorded it under the supposition that it was normal. In whatever way the error may have originated, it is only one out of many that are propagated even to the present day by the uninformed.

At the moment of writing, we read in one of our first-class ‘dailies,’ alluding to a brood of young vipers lately born at the Zoological Gardens: ‘The young viper comes into the world in the shape of an egg, and its first business is to push through the filmy membrane which envelops it in its imprisoned form.’ This is contrary to our accepted ideas, though partially true in this instance. The word viper is generally supposed to be derived from the Latin vipera, a contraction of vivipara, to produce alive. The above words therefore are inapplicable as a rule.

So far as was known in Aristotle’s time, only certain venomous species common in the countries with which classic writers were best acquainted did produce live young, and they were mostly what are still known as ‘vipers,’ a term restricted to these and explained as being derived from such signification.

Opportunities of study and of observation afforded in menageries and zoological gardens at the present day have caused the term viper as relating to gestation to be discarded, or many non-venomous snakes must be included, thus overthrowing all our notions of vipers. As was shown in the preceding chapters, the name is now associated with dentition.

German and French ophiologists affirm that the three distinctions of oviparous, viviparous, and ovoviviparous are founded on no other ground than the greater or less development of the foetus at the time of deposition.

The nature of the egg-covering or ‘shell’ has also to do with this. In eggs which take a longer time to mature or to ‘hatch,’ the external covering is thicker and more leathery; in those which are hatched either before or on deposition, the shell is thinner, more membranous. Always, however, there is a calcareous element in the shell, and the eggs are generally, but not invariably, linked together.

Heat and moisture are essential to the hatching of eggs. When at liberty the snake selects some spot among decaying leaves, or in a manure heap where decomposition produces sufficient warmth. In the tropics, where the sun’s rays alone suffice, a soft moist bed is more easily found, and here it is that immense broods are produced.

The period of gestation can scarcely be pronounced upon with certainty. It depends not only on the size of the snake, but on the degree of warmth that can be enjoyed as an assistant to mature the eggs. Schlegel mentions three or four months from copulation to the laying of eggs in the species indigenous to France. But as other circumstances combine to cause variations in these periods, it is very unsafe to fix upon the precise time of gestation.

Says Rymer Jones, ‘Reptiles do not sit (sic) upon their eggs, hence the latter have only a membranous envelope. In many of the reptiles which lay eggs, especially the Colubri (colubrine snakes), the young one is already formed and considerably advanced in the egg at the moment when the mother lays it; and it is the same with those species which may at pleasure be rendered viviparous by retarding their laying.’[129] The latter words are traced to Cuvier, and prove that this most remarkable power has long been recognised.

In the first few words of the above, Jones spoke of reptiles generally from toads to turtles; with the latter, soft eggs would certainly fare badly did they attempt to incubate them. Still the term ‘reptiles’ is misleading, because, as is now well known, some snakes do incubate, and some lizards are suspected of doing the same. Even our common ring snake has been found coiled upon her eggs.

Serpents are allied to birds in producing young from eggs, but in reptiles the eggs differ from those of birds in undergoing a sort of incubation from the very first; so that at whatever period a snake’s egg is examined, whether it has been laid or not, the embryo will be found more or less advanced. Sometimes in an egg just deposited, a perfectly formed foetus will be found. ‘Serpents are always oviparous,’ says Schlegel; ‘and it is a mistake to suppose that all venomous snakes produce live young, and all non-venomous kinds lay eggs. Neither has the diversity of generation any relation to the organization of the animal itself. Coronella lÆvis produces living young, but other coronellas lay eggs. In 1862, when very little was known of the Coronella lÆvis, Mr. Frank Buckland had one in a cage in London, which to the surprise of most persons produced live young ones. This may have been solely owing to her captivity and her retention of eggs till hatched. Some boas lay eggs, others are viviparous. In the latter case the young are enclosed in a thin membrane, which they tear or break at the moment of birth. In those that are a long while hatching, the tunic is of a thick, coriaceous texture, not easily ruptured. Thus, to sum up with one other authority, Der Hoeven: ‘In many serpents and lizards the development begins in the body of the parent before the egg is laid, and in some the membrane of the egg is broken by the young one before birth.’

This latter condition has been considered viperine, but even in a viper the young have been produced in a membrane. This was the case with Vipera nasicornis at the London Zoological Gardens, on Sunday, November 6th, 1881, that gave birth to forty-six viperlings. Some of them had no vestige of membrane clinging about them; others had, but burst it immediately and began to crawl; while yet others did not burst their ‘shell’ at all,—if indeed so filmy and thin a membrane could be called a shell,—but died within it. When the membrane burst, it was seen to collapse and shrivel up into nothing, as children’s air balls do when they are torn; but the texture of these balls is strong in comparison with the extreme tenuity of the viperine egg tunic. Yet it was strong enough to contain a young one, as in the case of those unbroken. There is no means of ascertaining the precise length of time this viper had been in captivity; but as her young ones had all such fully-developed fangs, and the precocity to strike and kill a mouse as soon as born, this was probably another case of postponed deposition. On a previous occasion, September 1875, a family of young vipers born at the Ophidarium were ‘some quite clean and others with the remains of the egg covering about them.’ The quotation from my notebook refers to the Daboia of India, ‘Russell’s viper’ (Vipera elegans). Still these may be exceptional and possibly abnormal cases, but are examples worth noting, and another proof of the many exceptions to what we are accustomed to believe invariable rules.

White, in his History of Selborne, mentions the capture of a viper in which he found fifteen young, the shortest being seven inches. They were active, spiteful, and menacing, and yet ‘had no manner of fangs that we could find, even with the help of our glasses.’

Mr. Frank Buckland tells of a man who cut open a string of snake’s eggs, and the young, thus prematurely introduced into the world, ‘showed fight.’

Of historical ophidians which have figured in many pages, first comes chronologically the Paris python, that in 1841 laid fifteen eggs and incubated them. She has already been alluded to in chap. iv., but claims further mention presently.

A python in the Amsterdam collection next hatched twenty-two eggs.

In 1862 a python at the London Gardens laid above a hundred eggs,—‘more than a bushel,’ according to the keeper,—and settled herself to hatch them. Much interest attaches itself to this lady’s history; but first to complete our list chronologically, the following harmless species in the London collection have within the last ten years produced live young, being examples of that ‘diversity of generation’ of which Schlegel speaks.

August 1872, the ‘seven-banded snake’ (Trop. leberis) had five young and some eggs at the same time.

June 1873, a Coluber natrix had seven young ones. (I cannot affirm positively that these were born alive; I think not, from an especial entry in my notebook concerning them; but the records of the Zoological Society in which I have sought for confirmation do not announce them as ‘hatched.’)

August 1873, a yellow Jamaica boa (Chilobothrus inornatus) gave birth to fourteen young ones, ten of which survived. They crawled up to the top of their cage as soon as they saw daylight, and showed signs of fight. One little aggressor struck at me when I held it, and tried to bite me through my glove,—an impertinence which was permitted in order to test its powers. It constricted my fingers as tightly as if a strong cord were wound round them, and when not thus occupied it wriggled and twisted itself about in such energetic contortions that I could scarcely hold it. The activity and daring of the whole fry proved their perfect development. On another occasion the same species produced eight, and on a third occasion thirty-three young ones, but of these dates I am not quite sure. In some cases a few eggs were produced at the same time, but they were hard and bad and of the consistency of soap. The manners and actions of the three equally well-developed families were similar. They were always on the defensive, and able to fight their own battles. When the keeper put his hand into the cage, they seized upon it and held on with their teeth so tightly that on raising it they hung wriggling and undulating like a living, waving tassel.

Another boa from Panama, on 30th June 1877, had twenty young, which displayed ability to take care of themselves forthwith by leaving the marks of their teeth on Holland’s fingers. These twenty were all produced during the night, or before the arrival of the keeper the next morning, and were lively and spiteful, biting any one who attempted to touch them, and sharply enough to draw blood. Mr. E. W. Searle, who described them in Land and Water at the time, July 1877, said: ‘This is probably the first recorded instance of the breeding of boa constrictors in captivity.’ He seemed also to infer that this proved the boa to be viviparous instead of oviparous, as ‘had been always understood.’ Having already known of cases of abnormal, and also of postponed production of eggs or of young, I ventured at the time to cite such cases in Land and Water, July 7, 1877, adding: ‘We must not too hastily conclude that because one boa constrictor produced a family of lively young ones, this species is invariably viviparous.’ Also in the Field, July 14, 1877, I suggested that ‘the circumstance might be received rather as a further example of snakes breeding under abnormal conditions,’—opinions further confirmed by subsequent observations.

The little fry were supplied with young mice, which they constricted as if they had served an apprenticeship; but the mother left them entirely to themselves, and betrayed no other unusual feelings than to hiss when disturbed. When they were seven weeks old, they in one night ate twenty-four mice and a few young rats between them. They all cast their first coat before they were a week old. The mother had been in the Gardens about eight years. All but one of this fine family were alive in the following November, and two are still living at the time of going to press, viz. ‘Totsey’ (illus. p. 201) and one brother.

The dates of these few following cases are a little uncertain, also exactly how many survived of those that were born.

A ‘seven-banded’ snake (Trop. leberis) had six.

A ‘chicken snake’ (Col. eximius).

A ‘moccasin snake’ (Tropidonotus fasciatus) had nine young ones. This species has sometimes produced young and eggs at the same time.

A ‘garter snake’ (Tropidonotus ordinatus).

A boa constrictor had eight pretty little active snakelings that at two days old pretended to constrict my fingers, and forcibly enough to prove their powers.

On two occasions at the Gardens within the time specified, hybrids have been born between Epicratis angulifer and Chilobothrus inornatus, and I can but think that occurrences of this nature must happen among snakes in their wild state occasionally, which may throw some light on the perplexities of classifiers.

In August 1878, three were born alive; and in recording the event the Secretary to the Zoological Society, P. Lutley Sclater, Esq., Ph.D., F.R.S., etc., writes that there can be no question as to the pairing of these two snakes, both in the same cage, and as there was no male Epicratis in the collection. Three were alive and six bad eggs were produced.

In September 1879, two more hybrids were born between the same pair; who, at any rate, remained constant to each other.

Of the venomous serpents that have fallen under my own notice at the Zoological Gardens, the little Indian viper (Echis carinata) had three young ones in July 1875. Only two survived a few weeks. They changed their coat at an early day, but ate nothing; nor did the mother, who soon died. One may mention here that the vipers in collections rarely do survive long after giving birth to young. This may be only owing to an unhealthy condition in captivity, but merits inquiry.

Four common adders (Vipera berus) and several broods of the Daboia have also been produced.

The African viper of the coloured illustration is another example, as having afforded opportunities for observation.

In point of numbers we find the families varying from three or four to upwards of a hundred. When the parent is in health, the young are produced easily and rapidly. Vipera nasicornis deposited her forty-six children within about three hours. A Java snake (though not in our London Ophidarium) produced twenty-four young ones in twenty minutes. Anaconda, in April 1877, on the contrary, exhibited considerable protraction, extruding bad eggs at irregular intervals for many days. She will form the subject of the next chapter.

Incubation, or the hatching of eggs by the maternal warmth, seems not to have been suspected by ophiologists until a comparatively recent date; but by the non-scientific, the barbarian and the untutored natives of hot countries, who see, but dream not that in future ages what they saw and incidentally spoke of would be of weight to the enlightened of as yet unexisting nations,—by such the fact was known long ere its worth as a fact was recognised. Yet, as has been already seen in these pages, evidence given without intent and purpose often is of scientific importance. Aristotle spoke of incubation; but with classic writers the difficulty of sifting fact from fable may cause the whole to be rejected.

We owe to Zoological Societies and menageries the confirmation of the couvaison of at least one species of serpents. Subsequently we are told, ‘The python only incubates,’ this snake being generally mentioned as the one exception; and only within a very few years has maternal affection been accredited to any others. Mr. P. H. Gosse was informed by the negroes in Jamaica of the habits of the yellow boa. Sir Joseph Fayrer was informed by the jugglers that ‘over and over again they had dug cobras out of their holes sitting on their eggs.’ Dr. E. Nicholson was informed ‘on trustworthy authority that the Hamadryad has been found coiled upon a nest of evidently artificial construction.’ He thinks snakes always watch over their eggs, and frequent the locality where they have deposited them. The keeper at the Gardens confirms this by his own observations. ‘They do care for their eggs in their own way,’ he assured me, and display unusual irritability and wildness at such times.[130] In menageries, however, their habits are always more or less artificial; they cannot seek spots for themselves, or exercise maternal instinct beyond doing the best they can under the circumstances. Anything in the way of extra indulgences, such as soft rubbish, moss, or sand, is duly appreciated when eggs are about to be deposited, and we find maternal ophidians resort at once to this.

In a footnote, vol. xvi. p. 65 of the Annales des sciences naturelles, we read:—‘Il parait que l’incubation des serpents est un fait si connu dans l’Inde, qu’il entre mÊme dans leur contes populaires. M. Roulin m’a fait remarquer dans le second voyage de Sindbad le marin (nouvelle traduction Anglaise des ‘Mille et une nuits’ par W. Lane, tom. iii. p. 20) le passage suivant: Alors je regardai dans la caverne, et vis, au fond, un enorme serpent endormi sur ses oeufs.’

Here again, by accident, an ophidian habit known in the 8th century has been revealed to the scientific of the 19th century.

In the 17th century, when the Royal Society was founded and scientific information of all descriptions was welcome in their published Transactions, the subject of serpent brooding appeared in those pages. In vol. i. p. 138, a few terse words exactly express what modern ophiologists have of late years verified. ‘Several have taken notice that there is a difference between the brooding of Snakes and Vipers; those laying their Eggs in Dung-hills by whose warmth they are hatched, but these (Vipers) brooding their Eggs within their Bellies, and bringing forth live Vipers. To which may be added,—That some affirm to have seen Snakes lye upon their Eggs as Hens sit upon theirs.’ This was published in 1665.

The truth of ophidian incubation in at least one species was finally established at the MusÉe d’Histoire at Paris in 1841, when Python bivittatus or Python À deux-raies—named from two black lines diverging from the mouth—incubated her fifteen eggs. This celebrated serpent has enriched zoological annals in several points of interest. She assisted to confirm the question of whether snakes drink, and, as will be seen, whether they will take dead food. In connection with the present subject, the observations made by M. Dumeril during her incubation in the months of May and June 1841 are of such interest that I will translate from a paper read at the Academy of Sciences in Paris, by M. Valenciennes, 19th July 1841, and published in the Annales des sciences naturelles, tom. xvi. 2^me sÉrie, p. 65. It will be remembered that M. Dumeril (to whom we are indebted for the most complete work on ErpÉtologie gÉnÉrale that graces the shelves of our Great National Library) was at that time Professeur d’ErpÉtologie au MusÉe de Paris, and specially charged with the management of that part of the menagerie.

M. Valenciennes began his paper by reminding his audience that the temperature of birds rises in various degrees during the period of incubation, proposing the questions, ‘Do reptiles not offer a similar phenomenon?’ ‘Do they never brood on their eggs?’ As far as was known of native reptiles, the answer would be in the negative. However, M. Lamarrepiquot, in his travels in Chandernagor and the isle of Bourbon, seems to show that a large serpent of India, and some other species, se plaÇait sur ses oeufs et les echauffait en developpant pendant ce temps une chaleur notable. Many eminent naturalists doubted this, until it was confirmed in the Paris python, in which was an example of prolonged and uninterrupted incubation for the space of fifty-six days.

M. Valenciennes proceeded to describe that she was in a cage with others, and that a temperature higher than the outside air was maintained. During January and February she coupled several times, and in February ate six or seven pounds of raw beef that was tied on to a live rabbit of middling size. Food offered her afterwards, for three weeks in succession, she refused; but, as described in chap. iv., she drank no less than five times during her brooding. Sloughing occurred on the 4th April. Generally gentle and quiet, she became excited on the 5th May, and tried to bite any one who approached her. Her condition being evident, she had been left alone and undisturbed in her cage; and at six o’clock on the morning of the 6th of May, laid an egg, fourteen others being deposited by half-past nine A.M. The eggs were soft at first, of an oval form, and an ashy-grey colour, but afterwards became rounder and of a clear white. They were all separate. She collected them in a cone-shaped pile, and rolled herself round them, so as to completely hide every one, her head being at the summit of the cone. For fifty-six days she kept perfectly motionless, excepting when manifesting impatience if any one attempted to touch her eggs. Notwithstanding this want of trustfulness on the part of the interesting invalid, M. Dumeril achieved some important experiments regarding her temperature.

Reptiles are ‘obedient to the surrounding temperature,’ we may repeat, but in the present instance there was warmth in her perceptible to the touch (une chaleur notable). The temperature of the cage was 20° (Reaumur?), that under the woollen coverlet where she reposed was 21°; but in her coils, where M. Dumeril inserted one of the best thermometers that could be procured, she was 41°, and always of a higher temperature by some 20°. Placing the thermometer either upon her or between the folds of her body, only a slight variation was perceptible, but it was invariably higher than the surrounding air.

On the 2nd of July one of the shells split (la coque s’est fendillÉe), and the head of a little python appeared. During that day the little creature only twisted about within its shell, now its head, now its tail being visible outside, and withdrawn again. The next day the wee snake made its debut altogether, and began to crawl about (s’est mise À ramper). It lost no time in exploring to the remotest corners of its blanket, and by degrees showed itself to the world. During the next four days eight were similarly hatched, the seven remaining eggs, at various stages of development, having apparently been crushed by superincumbent weight.

The mother, on the 3rd of July, ate six more pounds of beef, after her fast of nearly five months; but with the posterior part of her body still folded over the eggs. She then quitted them, and displayed no further care, having covered them for so long a time, and even defended them with such assiduity. From ten to fourteen days after being hatched, the young ones all changed their coats, and then ate some little sparrows, throwing themselves upon them, and constricting them like grown-up pythons.

M. Valenciennes drew attention to the circumstance that only in hot countries do serpents incubate their eggs, i.e. only the serpents indigenous to hot countries. In temperate ones, where the average warmth is insufficient, they resort to artificial heat; as, for instance, manure heaps, or decaying vegetation.

Thus was this important question settled, and the hatching of the young brood in Paris became a chronological era in ophidian annals.

When therefore, in January 1862, twenty-one years afterwards, a python seba in our own Gardens laid upwards of a hundred eggs, immense interest and curiosity were excited among the zoologists of the day, for here at home in London was a grand opportunity for observing the one only snake which at that time was supposed to exhibit any sort of maternal instinct. Plenty of damp moss had been supplied to her, the temperature maintained in the cage being supposed sufficient for her well-being. She pushed the moss into a kind of nest, and when the ‘long string of eggs’ were deposited, she arranged them in a nearly level mass, and then coiled herself over and around them so as to hide and cover them as much as possible. Sometimes she changed her position a little, and re-arranged her eggs, and in various ways rendered herself worthy of record.

Ophiologists had scientific facts to verify: this opportunity must not be neglected for ascertaining whether so cold a nature, and in midwinter, could produce sufficient warmth by lying there day after day upon her bushel of eggs. So thermometers were ever and anon thrust between her coils, or held close to her; first here, then there, after the example of M. Dumeril in Paris. Other disturbances in the way of cleaning out the cage and supplying her companion in captivity with food and water were angrily resented by the poor patient, who had no chance of the tranquillity that she would have sought for herself in her native tropics. Besides which, the chances against hatching were far greater in her case than in the Paris and Amsterdam pythons. The former saved only eight out of her fifteen, and here we had, in round numbers, one hundred, more than she could successfully cover at one time. Moreover, a most untoward accident happened one night by the tank overflowing among her eggs, necessitating a complete disturbance of them. What wonder, then, that she was irritable and even savage during the whole time of her incubation! One egg, examined fifteen days after it was laid, contained a living embryo, so there were hopes of some at least maturing. For more than seven weeks she remained patiently brooding, when all hope of hatching any of the eggs had vanished, and it became necessary to take them from her. This was done by degrees, and the task was no easy one. The keeper watched his opportunity to raise the sliding door at the back of the cage, make a snatch at those nearest him, and shut down the slide with celerity, or the exasperated mother would have seized him. He nearly got his arm broken more than once by the despatch he was compelled to use. Sometimes, so quick was she, that in thrusting down the slide she was nearly jammed by it. Holland protected himself by holding up a corner of the rug so as to hide himself when he had occasion to open the slide door; yet one day she ‘jumped’ at him, seizing the rug, and with a toss of her head jerking it back with such violence that a shower of the gravel came hailing upon the glass in front of the cage, to the consternation and alarm of the spectators gathered there, and who at the moment imagined the glass was broken, and that the infuriated reptile would be among them. But they were behind her; it was only towards the keeper that her fury was directed: he had taken away the last of her eggs. When, then, he shut down the slide, she kept her angry eyes fixed upon it for a long while. Presently she sought in her empty nest, upon which, so long as any eggs had remained to her, she had re-settled herself after each irruption. At last she took to her bath, in which she remained for a long while.

After the scenes witnessed during those seven weeks, no one could doubt the existence of maternal affection; and this was worth proving, as some authors would have persuaded us that snakes, and particularly the non-venomous ones, manifest total indifference regarding their eggs. The other important fact, an increased temperature, was also again observable, proving that a serpent can really hatch her eggs by the warmth of her own body.

Last summer, 1881, another python laid about twenty eggs at the London Ophidarium, but, alas! neither were any of that brood hatched. For future broods, now that the fact of a raised temperature has been proved, the next scientific triumph will be to develop the young ones, dispensing with thermometers, and substituting perfect tranquillity, with every possible aid and comfort to the mother.

That snakes under these peculiar circumstances do appreciate little ‘delicate attentions,’ ample proof has been afforded in the Jamaica ‘yellow boa’ (Chilobothrus inornatus), the species which on several occasions has produced broods in London, and the one in which Mr. P. H. Gosse verified the marvellous instinct of withholding its eggs when circumstances were not propitious for their deposition. This is one of the ‘Colubri’ alluded to by T. Rymer Jones, ‘which may at pleasure be rendered’ (i.e. render themselves) ‘viviparous by retarding their laying.’

But when Gosse published his work on Jamaica (1851), he did not appear to be aware of what Jones and Cuvier had said on this subject, but stated the result of his own observations. He had become convinced that this species of snake forms a sort of nest, and incubates its eggs; when subsequently, one that he had in captivity produced living young, he was staggered. ‘Is it possible,’ he wrote, ‘that a serpent normally oviparous, might retain the eggs within the oviduct until the birth of her young, when circumstances were not propitious?’

‘Is it possible,’ again asks an American naturalist, so lately as 1879,—‘can it be true that Heterodon platyrhinos and Tropidonotus sipedon’ (both harmless) ‘are sometimes viviparous and sometimes ovoviviparous?’ This writer, F. W. Cragin, had been told that the two above species were ovoviviparous (a word of no value as a definition), and he writes in the American Naturalist, vol. xiii. p. 710, that out of twenty-two eggs of Heterodon, ploughed up out of the sand in Long Island, one he put into alcohol to preserve it as found, and the others were hatched on the fourth day, showing that sometimes at least it is oviparous, as supposed are some of the EutÆnias.

Mr. Gosse describes one Jamaica boa in confinement, that was ill and inactive, refusing food. It was unusually vicious, and bit hard enough to draw blood, the effect of the fine teeth being like a severe cat-scratch. It rendered itself further offensive when disturbed, by emitting an insufferable odour, and at length gave birth to living young.

That this snake when at liberty lays eggs, he had seen, and in a nest of artificial construction. One that he knew of was excavated in a bank. The snake was seen issuing from a narrow passage just large enough to admit it. Dry, crumbled earth had been discharged at the entrance of the passage, where it lay in a heap. The bank being dug into, the passage was found to lead to a cavity lined with soft rubbish, leaves, etc., which must have been carried there. Mr. Gosse does not pretend to affirm positively that the snake constructed that secluded nest for itself. It might have done so, pushing out the mould by the lateral undulations of its body, as the burrowing snakes do, and carrying back the soft trash in its mouth or, if it only chose a nest formed by some other animal, this proved maternal care. There were eggs in the nest, the shell being like ‘white kid.’ ‘On snipping one, a clear glaire exuded, in which was a large, whitish vitellus, stained with blood vessels, and containing a young snake seven inches long, but immature.’ One foetus writhed. The foetus being formed and capable of motion, proved, Mr. Gosse thought, that the eggs had been some time laid. Incubation is a characteristic of that family, the author affirms. Of the various cases he knew, one female boa brought forth eleven snakes. In another snake that was killed, ten or twelve fully-formed young ones were found.

One of these ‘yellow boas’ in a private collection displayed unusual restlessness and uneasiness, crawling about its cage as if in search of something. Those who had the care of it suspected that she was with eggs, and supplied her with fine sand. This appeased her somewhat, and after twirling herself around to form it into a kind of nest, she laid some eggs. One of the same kind at the Gardens accepted gratefully some soft cotton wool which a lady brought for her and her young progeny, all of whom nestled themselves in it contentedly and speedily.

Two other noteworthy cases have to be recorded, but they shall form the subject of the ensuing chapters.