POLYGYRA ALBOLABRIS AND LIMAX MAXIMUS 259 



The position of the generative organs in the animal can be 

 clearly understood from plate 23, figure 9. 



The penis occupies the dorsal anterior part of the foot; the 

 vagina the anterior right lateral part. The receptaculum seminis 

 closely adheres to the prostate gland. The vas deferens is situ- 

 ated between and beneath the penis and vagiua; on account of its 

 great length being disposed in irregular folds. The prostate 

 gland and uterine canal enter the first volution of the animal and 

 are disposed alongside the pulmonary cavity. The albumen 

 gland lies between the large lobe of the digestive gland and the 

 stomach. The constricted, thread-like part of the hermaphroditic 

 duct crosses the stomach from the base of the albumen gland, 

 and the convoluted part of the duct lies in the inner margin of the 

 volution, alongside of a part of the stomach. The ovotestis, in 

 conjunction with the superior lobe of the digestive gland, occu- 

 pies all the apical parts of the animal. 



The generative organs of the other species of helicoid snails, 

 though varying in detail, are suificiently similar to those of 

 P. albolabris to enable the student to recognize them with- 

 out difficulty, with the exception of those of Gastrodonta 

 intertexta, G. gularis, G. ligera and G. s u p- 

 p r e s s a, which species have accessory organs, that will be de- 

 scribed later on. 



The vas deferens is usually about twice the length of the penis, 

 or less. InPolygyra exoleta it is longer^ but in no 

 species, as far as I am aware, is it as long as in P. a i b o 1 a b r i s. 

 InP. tridentata and in P. e x o 1 e t a it has the same form as 

 in P. albolabris, that is^ enlarged, glandular, annulated or 

 somewhat spiral in appearance at its beginning; while, on the 

 contrary^ inPyramidula solitaria it has this form at its 

 termination. In O m p h a 1 i n a f u 1 i g i n o s a it is for a great 

 part of its length expanded, so that its diameter is equal to that of 

 the penis. 



In some species, as in Polygyra auriculata and 

 P. s a y i, the penis is very long and bent on itself, while in others, 

 as Pyramidula solitaria, it is short, stout and clavate. 



