germ cells, and by them the whole somatic structure is rebuilt with but little change of detail from generation to generation. This phase of lire activity is still a mystery to us, for no attempted explanation seems adequate to account for the organizing power resident in the germ cells that accomplishes the familiar facts of repeated
k-X DO? A B F?ç. 73- Di?rams ?f the internal organ? of reproduction in insects A, the female otgans, ?mprising a pair ?f ??aries (Or), ea«h «omp?sed ?f ? group ?f ?g tubul?s (oe), a pair ?f ovidu«ts (DOv),and a median ourlet tube,?r v?ina (g?), ?ith usually a pair of «olleterial glands (CIÇI) dis«ha?ing into the ?agina, and a sperm roEeptade» ?r spermath?a (?p?), opening from the up?r surface of the latter B, the male o?ans, comprising a pair of restes (Tes) com?s? of spermatic tubules, a pair of s?rm ducts, or vasa deferentia (?D), a pair of s?rm vesicles (gS), and an outlet tube, or ductus ejaculatorius (DES, with usually a pair of mucous glands (MGI) discharging into the ducts of the sperm vesicles development which we call repr?uction._ When we can explain the repetition of buds along the twig, we may have a key to the secret of the germ cells?and possibly to that of organic evolution. The organs that house the germ cells in the mature insect consist of a pair of ovaries in the female (Fig. 73 A, Or) in which the eggs mature, and of a pair of testes in the [???l
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