120 INVERTEBRATE ZOOLOGY 
injure the nerve collar or reproductive organs. Notice that the 
connection of the cesophagus and the salivary ducts with the 
pharynx is near the dorsal wall of the latter organ. Observe 
the thick muscular tongue, the organ by means of which the 
animal grinds its food. Its surface is covered with a ribbon 
set with small teeth, called the radula. This can be easily 
pulled off with forceps. Mount it on a slide in water or 
glycerine and study its surface under a high power of the 
microscope. 
Exercise 6. Make a drawing of several of the teeth. 
The reproductive system. The snail is hermaphroditic, but is 
not self-fertilizing. The hermaphroditic gland, which at different 
times produces both spermatozoa and ova, is situated on the 
inner side of the smaller lobe of the liver. The hermaphroditic 
duct is a delicate, white, convoluted tube, which goes from the 
hermaphroditic gland to the albuminous gland, a large white body 
lying near the liver. From this organ the oviduct and vas 
deferens pass forward to the genital opening near the mouth. 
These canals are side by side and connected with each other for 
the first part of their course, but may be distinguished by the 
character of their walls, the oviduct having folded glandular 
walls, while the vas deferens is a narrow tube with thin walls. 
It is through the latter canal that spermatozoa pass out from 
the hermaphroditic duct, while the ova pass out through the 
oviduct, the glandular walls of which, together with the albu- 
minous gland, secrete the albumen which surrounds them when 
they are extruded. Near their forward end these two canals 
separate. The oviduct loses its glandular walls, becomes cylin- 
drical in shape, and expands to form the vagina. This is a thick- 
walled vessel with which are connected the following accessory 
genital organs: the receptaculum seminis, a small spherical organ, 
already mentioned, lying in the bend of the intestine and joined 
with the vagina by means of a long tube which lies along the 
