REPRODUCTIVE SYSTEM IN THE SNAIL. 63 



The prostatic or posterior part of the male system is a greatly 

 enlarged, cavernous and highly glandular conduit (PG) which 

 receives the filiform vas efferens into its posterior end and gives 

 off a short, thick, glandular tube, the beginning of the vas deferens, 

 from its globular anterior end. 



The vas deferens proper is a filiform, muscular tube lined with 

 ciliated columnar cells. Originating as a thick tube at the anterior 

 end of the prostate gland, it describes a tortuous course and 

 eventually enters the copulatory organ (CO/) where it terminates 

 in a short needle-pointed intromittent organ (/O). That part of 

 the vas deferens lying between the copulatory organ and the male 

 orifice is free within a cavity of the body, while that between the 

 male and female orifices lies just under the body wall. In the 

 living snail this tube is visible from its attachment at the female 

 orifice to its insertion in the copulatory organ and during copula* 

 tion it can be seen very distinctly moving in strong undulations. 

 Excised pieces of the living vas deferens writhe like pieces of a 

 living earth worm, thus demonstrating a function of its well- 

 developed muscular walls. 



At the time of copulation the copulatory organ is evaginated 

 through the male orifice, and after becoming turgid presents a 

 conical end with the intromittent organ extended as in Fig. 2. 



CONCLUSIONS. 

 The results of this investigation show that the anatomy of the 



J 



reproductive system in L. s. af>f>ressa is very similar to that in L. 

 stagnalis, as described by Baudelot. However, it is also shown 

 that cross-fertilization probably is not the normal mode of re- 

 production in either form. Spermatozoa are placed in the sperm 

 receptacle during copulation and in order to inseminate the ova they 

 must swim the length of the female conduit, through the viscous 

 substances secreted by the albumen gland, egg membrane gland 

 and mass membrane gland and penetrate the ovum before it is 

 covered with albumen. This would be not later than the arrival 

 of the ovum at the convoluted uterus. Whether these viscous 

 secretions prevent or even hinder the movements of the sper- 

 matozoa is not known. However, sperms in the albumen of L. 

 palustris eggs which have been oviposited are apparently helpless 

 with regard to locomotion. 



