IO2 Invertebrate Zoology. 



the last pair of thoracic appendages. 1 Do you find the 

 anus ? 



Remove and make a drawing of one of the appen- 

 dages. 



Before the body has been opened, the transparency of the 

 integument permits the location of several internal organs. 

 A large dark-colored area on either side, near the base of 

 the cone, marks the position of the " hepatic glands." A 

 smaller, orange-colored area near the base of the most 

 anterior filament is the anterior end of the vas deferens. 

 On the ventral side the muscular apparatus and the gan- 

 glionic chain are beautifully shown. 



Carefully remove the right half of the shell, and trace 

 the folds of the integument into the peduncle. The pedun- 

 cle is a prolongation of the head, the anterior (first] anten- 

 na of the larva having entered into its formation. 2 The 

 second antenna are, in the adult, aborted. 



At the summit of the oral cone a large transverse fold will 

 be found to bound the mouth anteriorly and to bear at each 

 end a triangular "scale-shaped" piece. The mandibles and 

 first maxilla bound the mouth laterally, while the second 

 maxilla are partially fused and form a lower lip. Both 

 mandibles and first maxillae have strong cutting edges. 



Digestive System. Carefully opening the animal along 

 the lateral line, note that a funnel-shaped tube leads from 



1 The abdomen is greatly reduced. It is represented on the dorsal 

 side by a pair of small terminal flaps which cover the anal opening, 

 while on the ventral side it supports the intromittent organ. 



2 The first antennae bear the so-called " cement glands," the secre- 

 tion of which enables the larva to attach itself. In the adult these 

 glands are to be found in the substance of the peduncle occupying a 

 position in its dorsal portion. 



