42 ASTERIAS VULGARIS. 



using a scalpel to free it, in the region of the disc, from any adhering 

 organs. Place the specimen in a large pan or dish and cover with 

 water. 



INTERNAL ANATOMY. Study the internal organs, observing the 

 following relations and parts: 



a) A large, much-wrinkled, five-lobed pouch, the stomach, cen- 



trally located. This was attached to the aboral wall by a short 

 conical intestine ending in the anus near the center of the disc. 

 The intestine and anus are probably not functional. Locate 

 the latter if possible. 



b) Connected with the intestine is a small, irregularly branched 



appendage, the intestinal ccecum. It may have been torn 

 away with the aboral wall. 



c) Opening into the upper, pyloric, part of the stomach are five ducts 



leading from the two-lobed hepatic cceca occupying the arms. 

 The function of the cceca is to secrete a digestive fluid. They 

 were attached to the aboral wall by light threads and films of 

 connective tissue, the mesenteries. 



d) Beneath the cceca (which, unless they remained attached to the 



roof, may be removed in one or two arms), in the furrow on either 

 side of the ambulacral ridge, are the five pairs of reproductive 

 organs. These are more or less well-developed according to 

 conditions for breeding and the age of the animal. In general 

 appearance they differ but little in the male and female, although 

 the ovaries sometimes have a light yellow color and are more 

 voluminous than the white testes of the male. The right lobe 

 or glandular mass in each arm unites with the left in the adjacent 

 arm to open externally by a common duct in the space between 

 two rays. This duct is at the point where the gland is attached 

 to the dermal wall. 



e) The retractor muscles, a pair attached to each lobe of the stomach 



and to the corresponding ambulacral ridge. These serve to pull 

 the stomach back into the body after it has been rolled out of the 

 mouth to envelop food. 



