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 



__-Tes 



VD 



VS 



C1G1 



Fie. 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 (ot), a pair of oviducts (DOv), and a median outlet tube, or 

 vagina (fg) t 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 (^D), a pair of sperm vesicles 

 (yS), and an outlet tube, or ductus ejaculatorius {DE), with usually a pair of 



mucous glands (MG1) 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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