IV.l THE COMMON SNAIL. 3OI 



transfer /// toto to a glass slide. Cover and ex- 

 amine in water under a low power. It appears as 

 a conspicuous round vesicle, lodging a refractive 

 black-looking granular contents. 



Examine under a high power. It is seen to 

 consist of a small sac (oiocyst) closed on all sides 

 and in no way connected with the exterior. It is 

 filled with a fluid contents, in which are suspended 

 a large number of small oval calcareous corpuscles 

 or otoliths. Trace the passage of the auditory 

 nerve into the vesicle. 



K. The reproductive elements. 



Remove a small piece of the ovotestis, and mount in 

 aqueous solution of Eosin. Examine under a low power 

 and note — 



a. The hermaphrodite follicles ; small coecal diverticula 

 r of the ovotestis, from the epithelial lining of which 



the sexual products are derived. They are arranged 

 i in grape like aggregates. 



; The appearances met with will be found to vary 



; with the season of the year. If spermatogenesis is 



\ going on there will be found, floating in the central 



cavity of each follicle, spermatozoa in all stages of 

 \ development. If the ova are undergoing maturation, 



they will be found, in all stages, still adherent to 



the germinal epithelium. 



Crush under the weight of a cover-glass and examine 

  under a high power. 



a. The ripe spermatozoa. Each is an elongated fili- 

 form body, bearing a small head-like enlargement 

 at one end. They are commonly met with in 

 aggregates. 



