. Evolution and animal life; an elementary discussion of facts, processes, laws and theories relating to the life and evolution of animals . FIG. 126.—Conjugation of Noctiluca, a one-celled ani-mal: A, Two individuals just fusing; B, the samewith cytoplasm wholly fused and nuclei lying closelytogether; C, the two nuclei in closer fusion; D, the be-ginning of fission. (After Ischikawa.) GENERATION, SEX AND ONTOGENY 221 ents, although it may be slight and imperceptible, is in-sured. Sex is a condition of nature which is one, at least,of the causes of FIG. 127.—Conjugation of the infu
. Evolution and animal life; an elementary discussion of facts, processes, laws and theories relating to the life and evolution of animals . FIG. 126.—Conjugation of Noctiluca, a one-celled ani-mal: A, Two individuals just fusing; B, the samewith cytoplasm wholly fused and nuclei lying closelytogether; C, the two nuclei in closer fusion; D, the be-ginning of fission. (After Ischikawa.) GENERATION, SEX AND ONTOGENY 221 ents, although it may be slight and imperceptible, is in-sured. Sex is a condition of nature which is one, at least,of the causes of FIG. 127.—Conjugation of the infusorian, Ynrti>eUa nebulifera; the smaller individualat the right may be regarded as the male. (After Weismann.) As we have seen, almost every species of animal is repre-sented by two kinds of individuals, males and females. In thecase of many animals, especially the simpler ones, these two
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