Soma (body), the body as distinguished from the germ-plasm. From this point of view every individual consists of only two parts,—germ-plasm and soma or somatoplasm.
Trait, a term used by geneticists as a synonym of "character."
Unit-Character, in Mendelian heredity a character or alternative difference of any kind, which is apparently not capable of subdivision in heredity, but is inherited as a whole, and which is capable of becoming associated in new combinations with other characters. The term is now going out of use, as it makes for clearer thinking about heredity to fix the attention on the factors of the germ-cells instead of on the characters of the adult.
Variation, a deviation in the size, shape, or other feature of a character or trait, from the mean or average of that character in the species.
Vestigial (footstep), a term applied to a character which at some time in the evolutionary history of the species possessed importance, or functioned fully, but which has now lost its importance or its original use, so that it remains a mere souvenir of the past, in a degenerated condition. Example, the muscles which move a man's ears.
Zygote (yolk), the fertilized egg-cell; the united cell formed by the union of the ovum and spermatozoön after fertilization.
Zymotic, caused by a microörganism,—a term applied to diseases. Example, tuberculosis.