INSECTS
germ cells, and by them the whole somatic structure is rebuilt with but little change of detail from generation to generation. This phase of life 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
Fig. 73. Diagrams of the internal organs of reproduction in insects
A, the female organs, comprising a pair of ovaries (Ov), each composed of a group of egg tubules (ov), a pair of oviducts (DOv),and a median outlet tube, or vagina (Vg), with usually a pair of colleterial glands (ClGl) discharging into the vagina, and a sperm receptacle, or spermatheca (Spm), opening from the upper surface of the latter
B, the male organs, comprising a pair of testes (Tes) composed of spermatic tubules, a pair of sperm ducts, or vasa deferentia (VD), a pair of sperm vesicles (VS), and an outlet tube, or ductus ejaculatorius (DE), with usually a pair of mucous glands (MGl) discharging into the ducts of the sperm vesicles
development which we call reproduction. 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, Ov) in which the eggs mature, and of a pair of testes in the
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