Page:Insects - Their Ways and Means of Living.djvu/154



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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