General principles of zoology . ogical and ananatomical. Physiologically importantis the fact that eggs and spermatozoabehave like excreta; being substanceswhich are no longer destined for the useof the individual, but must reach theexterior in order to become anatomical cause is the relationto the body-cavity; , it is alwaysthe case that a urino-genital systemis formed only in animals in whichthe germinal epithelium arises fromthe epithelium of the body-cavity,and in which the kidneys, or theirrudiments, stand permanently, in con-nection with the body-cavity andthus form the
General principles of zoology . ogical and ananatomical. Physiologically importantis the fact that eggs and spermatozoabehave like excreta; being substanceswhich are no longer destined for the useof the individual, but must reach theexterior in order to become anatomical cause is the relationto the body-cavity; , it is alwaysthe case that a urino-genital systemis formed only in animals in whichthe germinal epithelium arises fromthe epithelium of the body-cavity,and in which the kidneys, or theirrudiments, stand permanently, in con-nection with the body-cavity andthus form the natural outlet for its products. Whetherthe accessory sexual parts are portions of the excretoryorgans or are independent structures, they have in theanimal series a definite arrangement conditioned by theirfunction (Fig. 70). Canals lead from the sexual glandsto the exterior, the oviducts in the female, the vasa dc-ferentia in the male (and the hermaphroditic duct from thehermaphroditic gland). Oviduct and vas deferens may be. FIG. 70.—Sexual apparatus ofVortex viridis. ( From )t, testicle ; vd, vasa defer-entia ; vs, vesicula semina-lis ;/, penis ; a, ovary withoviduct ; «, uterus ; r,vagina ; rs, receptaculumseminis; gv, yolk-glands. 144 GENERAL PRINCIPLES OF ZOOLOGY. provided with sac-like evaginations which serve for the re-ception of the semen. In the oviduct, these are called rc-ccptacula scminis, in the vas deferens vesiculceseminales ; theformer give lodgment to semen which has entered thefemale sexual passages during coition, the latter to semenwhich has been formed in the true testes. Accessory Sexual Apparatus.—The terminal portionof the vas deferens is often very muscular and is called theductns ejaculatorius; it may be evaginated as a penis orcirrus, and then projects beyond the surface of the terminal portion of the oviduct is usually widened sothat two portions may be distinguished, the uterus, whichharbors the eggs duri
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1896
