Introduction to Animal Morphology. 301 



and has appended to it a multifimbriated prostate. 



The end of the vas deferens is muscular, elongated 



as a penis often with a long flagel- Y\g. n. 



lum. The spermatozoa are united by 

 albuminous matter into masses or sper- 

 matophores. In Helicidae there is ap- 

 pended to the male organs an eversi- 

 ble sac, whose papillary mouth is close 

 to the opening of the mucous glands ; 

 within this the epithelium is calcified 

 into a sharp quadrangular dart, vary- 

 ing in shape in different species. This 

 is everted, and is used previous to the 

 mutual impregnation of two indivi- ^ ^'^f'T''^* 



J^ '-' Kcproductive Organs 



duals as an organ of irritation. Its i,^'I^h'o°iiSanZ: 

 use lasts about two hours in a snail, bHlted'pro^tat';^'"; 

 and is followed by a 5-7 minutes' im- gLndr^.'recepflcui^m 



■ • T T • J.1 J. • T • seminis ; ^, dart sac; 



pregnation. in Limax the two mdivi- e, uterus. 

 duals twist spirally round each other in coitu. Self- 

 impregnation has only been noted in Tergipes Ed- 

 wardsii, and Limnaea auricularis, in the whole class. 



Heteropods are dioecious : the penis of the males is 

 a projection of the body wall with no sac, but with a gland- 

 ular extremity, on the right side ; and in Pterotrachea a 

 mesopodial sucker is added. The lobed testis occupies the 

 hinder part of the nucleus, and from the opening of the vas 

 deferens a ciliated groove leads to the testis. In the females 

 there is an ovary in the same position as the testis (often only 

 distinguishable from it by its contents), an oviduct, albumen 

 gland, uterus and vagina. Prosobranchs are m.ostly dioecious 

 (except Chiton and Valvata). Some (Cymba, Littorina, 

 Paludina), like the Pulmonates Plicaphora ventricosa, 

 Clausilia similis, Pupa umbilicata and marginale, Helix ru- 

 pestris, and some species of Achatinella and Vitrina, are 



