144 HERMAPHRODITE MOLLUSCA, GENERATIVE ORGANS cuav. 



Hermaphrodite MoUusca. — (&) Digonoiwra. — As an example 

 of tlu; J)l(/()ii()2)oiu or lu'iiiiaphrodite Mollusca with separate 

 generative apertm-es for the male and female organs, we may 

 take the connnon Limnaea stagnalis (Fig. 55). It will be seen 

 from the figure' that the relative positions of the hermaphrodite 

 gland and duct, and of the albumen gland, are the same as in 

 Helix. When the oviduct parts compan}- from the vas deferens, 

 it becomes furnished with several accessory glands, one of which 

 (Gi.E.) probably serves as a reservoir for the ova, and answers 

 more or less to a uterus. The tube leading to the spermatheca 



Fig. 55. — Genitalia of Limnaea stagnalis 

 L. (from a dissection by F. B. Stead), 

 X 2. 



A.G, alluuiu'n gland. 



Ac.G, acce.ssory yland. 



F.O, female orifice. 



GI.E, glandular enlargement. 



H.D, liernianlirodite duct. 



H.G, liennaphrodito gland. 



Li, liver. 



M.O, male orifice. 



P, jienis sac. 



Pr, prostate. 



B.M, retractor muscle of jienis. 



Sp, si)enuatlieca. 



V.D, vas deferens. 



is short, and there is no divergent coecum. The female orifice 

 lies near to the external opening of the Itranchial cavity. The 

 ^'as deferens, which is very long, is furnished witli a large prostate 

 gland. The penis sac is greatly dilated, and there is no fiagellmn. 

 The male orifice is behind the right tentacle, slightly in advance 

 of the female orifice (ccmipare Fig. 102). 



Most of the 0^)istliohrancliiata, but not all, liave separate sexual 

 orifices. Numerous variations from the type; just described will 

 be found to occur, particularly in the direction of the develop- 



