GASTROPODA. 



377 



sac giving off branching glandular tubes (Chitonidae, some Nudi- 

 branchs). 



Pericardial glands are present as differentiations of the lining of 

 the pericardium. 



Generative organs. The Streptoneura are dioecious, with the 

 exception of Valvata, Marsenina, Onchidiopsis, Odostomia, and Ento- 

 concha ; the Euthyneura and these five genera are hermaphrodite. 



In the dioecious forms there is usually but little to mark the 

 sexes externally, unless a penis be present. The generative gland 



a d 



i -n 



FIG. 297. Diagrams illustrating the arrange- 

 ment of the kidneys and pericardium in 

 Prosobranchiate Gastropods (from E. Per- 

 rier, after R. Pcrrier). a, Lamellibranchs. 

 6, Fissurella. c, Haliotis. d, Patella, c, Pec- 

 tinibranchs. g gonad ; i rectum ; k reno- 

 pericardial opening; n duct of right kidney 

 (of left in e), n' duct of left; o right, o' 

 left auricle (except in d and e, in which o is 

 the left auricle); p pericardium; r right, 

 /' left kidney (except in e, where r is the left 

 kidney, and r 1 a blood gland) ; v ventricle. 



