228 MORPHOLOGY OK INVERTEBRATE TYPES 



copulation, opens also into the genital cloaca. The vas def- 

 erens separates from the female duct at the point where the 

 vagina begins and soon leads into the coiled penis which opens 

 into the vestibule. The penis is provided with a retractor penis, 

 a powerful muscle which arises from the dorsal body wall some- 

 what in front and to the left of the common retractor of the 

 tentacles. The penis is situated above the stomach and passes 

 under the retractor of the right posterior tentacle before it 

 reaches the vestibule. We have seen already that the vestibule 

 opens to the outside on the right side of the animal, in front of 

 the shield. This is the common genital opening. When two in- 

 dividuals come together in the act of copulation, the penis of 

 the male is protruded through his common genital opening and 

 is introduced into the bursa copulatrix of the female through her 

 common genital opening. The eggs undergo an abbreviated 

 development in which the characteristic larval stage of gaster- 

 opod molluscs is considerably modified and difficult of recogni- 

 tion. 



Instructions 



1. Place a specimen in a dissecting tray with water and make a 

 half page drawing of its right side. Label foot, mantle, pneumo- 

 stoma, genital opening (in front of mantle, behind tentacles), 

 anterior right tentacle, posterior right tentacle with eye (if 

 everted) . 



2. Make a large drawing showing the front view of Limax. 

 Label the four tentacles, mouth, upper lip and the cleft lower 

 lip. 



3. Make an incision with scissors along the left side just 

 above the foot and extending as far as the head. Make another 

 incision along the right side, but extending only to the posterior 

 edge of the shield; remove the dorsal body wall back of the shield 

 by a transverse incision. Pin down the foot. Carefully turn 

 the shield over to the right, cutting the aorta, retractor penis 

 and retractor of the tentacles and freeing the rectum. Make a 



