GLOSSARY

Acquired Characters, traits developed in the body through changes in environment or function, in contra-distinction to those which have their specific causes in the germ-cells.

Adaptation (L. ad, to; aptus, fit), fitness to environment.

Albinism (L. albus, white), a condition of deficiency in pigment.

Allelomorph (Gr. allelon, of one another; morphe, form), one of a pair of alternate Mendelian characters.

Ameba (Gr. amoibe, change), a primitive single-celled animal.

Amphibian (Gr. amphi, both; bios, life), capable of living both on land and in water.

Anthropoid (Gr. anthropos, man; eidos, form), man-like.

Aristogenic (Gr. aristos, best; genesis, origin), pertaining to the genetically most desirable human strains.

Association Areas, those regions of the brain in which presumably the higher mental processes are effected.

Atavism (L. ad, before; avus, grandfather), a return in one or more characters to an ancestral type. See p. 8 for restricted modern usage.

Atrophy (Gr. a, negative; trophe, nourishment), a wasting away of a part of a living organism.

Axon (Gr. axon, axis), the process from a nerve cell which becomes a nerve fiber.

Binet-Simon Scale, a series of tests graded to age and previous training of the average normal child, much used in measuring mental deficiency.

Biology (Gr. bios, life; logos, discourse), the study of life and of living things.

Biometry (Gr. bios, life; metron, measure), the study of biological problems by means of statistical methods.

Blastomere (Gr. blastos, germ; meros, part), one of the early cells formed by the division of the ovum.

Blastophthoria (Gr. blastos, germ; phtheiro, destroy), deterioration of the germ as the result of direct pathogenic or other disturbing agents.

Blending Inheritance, inheritance in which the characters of the parents seem to blend in the offspring.

Cacogenic (Gr. kakos, bad; genesis, origin), pertaining to genetically undesirable human strains.

Cell, the fundamental unit of structure in plants and animals.

Centrosome (Gr. kentron, center; soma, body), a small body which functions in indirect cell-division.

Character, any distinguishing feature, trait or property of an organism.

Chemotropism (chemical and tropism), defined, p. 198.

Chromatin (Gr. chroma, color), deeply staining substance of the cell-nucleus.

Chromosomes (Gr. chroma, color; soma, body), characteristic deeply staining bodies, typically constant in number and appearance in each species of animal or plant, which appear in the cell during indirect division.

Chromotropism (Gr. chroma, color; trope, turning), defined, p. 198.

Cleavage, the division of the egg-cell into many cells.

Congenital (L. con, together; gigno, bear), present at birth.

Conjugation (L. con, together; jugum, yolk), the union of germ-cells or unicellular individuals for reproduction.

Constructive (or positive) Eugenics, a system of securing a superior race through propagation of the fittest individuals.

Cortex (L. cortex, bark), the outer or investing layer of the brain.

Cytoplasm (Gr. kytos, cell; plasso, form), the protoplasm of the cell outside of the nucleus.

Daltonism, the commonest form of color-blindness in which the affected individual is unable to discriminate between red and green.

Dendrites (Gr. dendron, tree), branching processes which spring from nerve-cells.

Determiner (L. determinare, to determine), the distinctive cause or unit in a germ-cell which determines the development of a particular character in the individual derived from that cell. The terms gene and factor are sometimes used as synonyms of determiner.

Dihybrids (L. di, two; hybrida, mongrel), the offspring of parents differing in two characters.

Diploid (Gr. diploos, double; eidos, form), the dual or somatic number of chromosomes.

Dominant Character (L. dominare, to be a master), a character from one parent which manifests itself in offspring to the exclusion of a contrasted character from the other parent.

Drosophila, a genus of fruit-flies of which there are several species.

Duplex (L. duo, two; plico, fold), the condition in which a character is represented by two determiners, one from each parent.

Electrotropism (Gr. electron, amber; trope, turning), defined, p. 198.

Embryo (Gr. embryon), the young organism in its earliest stages of development.

Embryogeny (Gr. embryon; genesis, generation), the development of the embryo.

Eugenics (Gr. eugenes, well-born), the science relating to improvement of the human race through good breeding.

Factor, the determiner of a particular hereditary character.

Feeble-Mindedness, deficiency in mental development. For grades, see p. 244.

Fertilization, union of the sexual cells.

Fetus (L. feuere, to bring forth), the unborn young animal in its later (after the second month in man) stages of development.

Flagellum (L. flagellum, little whip), a vibratile, thread-like organ of locomotion.

Gamete (Gr. gamos, marriage), a mature germ-cell.

Genetics (Gr. genesis, origin), the science which deals with heredity and the origin of individuals in general.

Genotype (Gr. genea, race; typto, strike), the germinal constitution of an organism.

Geotropism (Gr. ge, earth; trope, turning), defined, p. 198.

Germ-Cell, a reproductive cell.

Germinal Variations, variations which owe their origin to some modification in the germ-cells.

Germ-Plasm, the material basis of inheritance.

Gonad (Gr. gonos, generation), a germ-gland.

Haploid (Gr. haploos, single; eidos, form), the single or reduced number of chromosomes as found, for instance, in the mature germ-cells.

Heliotropism (Gr. helios, sun; trope, turning), defined, p. 198.

Heredity (L. heres, heir), resemblance of individuals to their progenitors based on community of origin.

Heritage (L. heres, heir), all that is inherited by an individual.

Heterozygote (Gr. heteros, other; zygon, yolk), an individual produced through the union of germ-cells which are unlike in one or more determiners. Adjective, heterozygous.

Homozygote (Gr. homos, same; zygon, yolk), an individual produced through the union of germ-cells which are alike in determiners. Adjective, homozygous.

Hybrid (L. hybrida, mongrel), the offspring of parents which differ in one or more characters.

Identical Twins, twins which show identical inborn characters, both having come presumably from the same ovum.

Idiot (Gr. idios, peculiar, private), defined, p. 244.

Imbecile (L. imbecillis, weak), defined, p. 244.

Inheritance (L. in, in; heres, heir), the sum of all characters which are transmitted by the germ-cells from generation to generation.

Inhibitor (L. in, in; habeo, hold, have), that which checks or restrains.

Instinct (L. in, in; stingno, prick), defined, p. 203.

Intra-uterine (L. intra, within; uterus, the womb), within the womb.

Irritability (L. irrito, excite), the property of responding to stimuli.

Linin (L. linum, flax), filaments of the cell-nucleus not readily stained by dyes.

Luetin Test (L. lues, pest), a test for syphilis; see p. 188.

Mammals (L. mamma, breast), warm-blooded, hairy animals which suckle their young.

Maturation (L. maturus, ripe), the final stages in the development of the sex-cells characterized by two divisions in one of which the number of chromosomes is reduced by one-half.

Mendelian, Mendelism, referring to Mendel, the founder of a theory of heredity. See p. 67.

Metazoa (Gr. meta, over; zoon, animal), all animals higher than the protozoa.

Mitosis (Gr. mitos, thread), indirect nuclear division, characterized by the appearance of a fibrous spindle and a definite number of chromosomes. The latter split to form daughter chromosomes which diverge to the poles of the spindle to form parts of the new nuclei.

Mongolian, a type of feeble-minded individual, see p. 248.

Monohybrid (Gr. monos, single; L. hybrida, mongrel), the offspring of parents, differing in one character.

Moron (Gr. moros, foolish), defined, p. 244.

Mutations (L. mutare, to change), abrupt, inheritable germinal variations. Frequently though not necessarily they are changes of considerable extent.

Neural (Gr. neuron, nerve), pertaining to the nervous system.

Neuron (Gr. neuron, nerve), a nerve-unit consisting of a nerve-cell with branching processes called dendrites and an axon or axis cylinder process which gives rise to a nerve fiber.

Neuropathic (Gr. neuron, nerve; pathos, suffering), relating to disease of the nervous system.

Nucleolus (L. dim. of nucleus), a well-defined body found within the nucleus of a cell.

Nucleus (L. nux, a nut), the central organ of a cell.

Nulliplex (L. nullus, not any; plico, fold), the condition in which no determiners of a given character exist in a particular individual.

OÖcyte (Gr. oon, egg; kytos, cell), the ovarian egg in one stage of development.

OÖgenesis (Gr. oon, egg; genesis, origin), the development of ova from primitive sex-cells.

OÖgonium (Gr. oon, egg; gonos, generation), a primordial egg-cell.

Ovary (L. ovum, egg), the organ in which the egg-cells multiply and are nourished.

Ovum (L. ovum, an egg), the female sex cell.

Parthenogenesis (Gr. parthenos, virgin; genesis, origin), development of an egg which has not united with a male gamete.

Phenotype (Gr. phaino, show; typto, strike), the existing type of individual irrespective of hereditary possibilities which may reside in it undeveloped.

Phototropism (Gr. phos, light; trope, turning), defined, p. 198.

Placenta (L. placenta, a flat cake), the organ by which the fetus of the higher mammals is attached to the uterine wall of the mother for purposes of nourishment, respiration and excretion. In it the maternal and fetal blood, although not intermingling, are brought into such close proximity that an interchange of dissolved substances is possible.

Polar Bodies, the minute cells which are separated from the egg in its maturation divisions.

Primate (L. primus, first), the highest order of animals, including monkeys, apes and man.

Pronucleus, the nucleus of the mature ovum or sperm-cell.

Protoplasm (Gr. protos, first; plasma, form), the essential living substance.

Protozoa (Gr. protos, first; zoon, animal), single-celled animals or animals composed of cells not separable into different tissues.

Psychical (Gr. psyche, the soul), pertaining to the mind.

Recessive Character (L. recessus, a going back), a character from one parent which remains undeveloped in offspring when associated with the corresponding dominant character from the other parent.

Reduction Division, a division of the maturing germ-cells in which the dual or somatic (diploid) number of chromosomes is reduced to the single (haploid) number.

Reflex Action (L. re, back; flectere, bend), an automatic response of the nervous and motor mechanism of the body.

Restrictive (or negative) Eugenics, a system of improving the human race by preventing reproduction of the unfit.

Reversion (L. re, back; verto, turn), the reappearance of ancestral traits which have for some generations been in abeyance.

Rheotropism (Gr. rheo, to flow; trope, turning), defined, p. 198.

Salpingectomy (Gr. salpinx, trumpet; ectome, cutting out), removal of part or all of a Fallopian tube (oviduct).

Segregation (L. se, aside; grex, flock), separation.

Sex Chromosome, a special chromosome which is supposed to be concerned in the determination of sex.

Sex-Linked Characters, defined, p. 60.

Simian (L. simia, ape), ape-like.

Simplex (L. sim, same; plico, fold), the condition in which a character is represented by a determiner from only one of the two parents.

Soma (Gr. soma, body), the body considered apart from the germ-cells.

Spermatid (Gr. sperma, seed), a cell resulting from the last division of the germ-cell in spermatogenesis. It transforms into the spermatozoon.

Spermatocytes (Gr. sperma, seed; kytos, cell), cells concerned in the maturation divisions of the male germ-cells.

Spermatogenesis (Gr. sperma, seed; genesis, origin), the development of spermatozoa from primitive sex-cells.

Spermatogonium (Gr. sperma, seed; gonos, generation), a primordial sperm-cell.

Spermatozoon (Gr. sperma, seed; zoon, animal), the functional male sex-cell.

Spindle, a fibrous organ formed in indirect cell-division.

Spireme (L. spira, coil), a characteristic stage preliminary to indirect cell-division in which the chromatin material of the nucleus appears in the form of a skein of filaments.

Stereotropism (Gr. stereos, solid; trope, turning), defined, p. 198.

Sterilization (L. sterilis, barren), deprivation of reproductive power. For methods, see p. 322.

Synapse (Gr. syn, together; hapto, unite), the coming in contact of the processes of one nerve cell with the processes or body of another.

Synapsis (Gr. syn, together; hapto, unite), union of the chromosomes in pairs preliminary to the reduction division.

Telegony (Gr. telegonos, born far away), the supposed influence of an earlier sire on offspring born later of the same mother to a different sire.

Thermotropism (Gr. thero, heat; trope, turning), defined, p. 198.

Thigmotropism (Gr. thigmo, touch; trope, turning), defined, p. 198.

Toxin (Gr. toxicon, poison), poisonous compounds of animal, vegetable, or bacterial origin.

Tropism (Gr. trope, turning), the automatic directing of an organism toward or away from a source of stimulus.

Unit-Character, a character which behaves as an indivisible unit in heredity.

Vasectomy (L. vas, vessel; ektome, cutting out), removal of a portion of the vas deferens (duct for conveying spermatozoa).

Vestigeal (L. vestigium, footstep), representing organs which existed once in a more developed condition.

Volvox (L. volvo, roll), a small fresh-water organism occurring in spherical colonies.

Wasserman Reaction, a test for syphilis, see p. 188.

X-Element, same as sex-chromosome.

Zygote (Gr. zygon, yolk), the product of the union of two gametes.