Branch Arthropoda 59 



ries. The testes are a pair of three-lobed bodies, gen- 

 erally white. If testes are present, find the ducts 

 leading from them to the external openings which 

 have already been found. The ovaries are a pair of 

 long, two-lobed bodies. If these are present, find their 

 ducts. Remember that only ovaries or testes will be 

 found in an individual, never both. 



XIII. — Digestive System. Remove the reproductive 

 organs, and the most conspicuous portion now ex- 

 posed will be the digestive glands. Find the ducts by 

 which their contents are emptied into* the small intes- 

 tine. The stomach is the hard-walled receptacle just 

 in front of these glands. It passes anteriorly into the 

 oesophagus, and posteriorly into the small intestine. 

 Pass the forceps through the mouth into the oesopha- 

 gus, and watch its passage to the stomach. The 

 very short small intestine expands into the large intes- 

 tine which terminates in the anal opening in the telson. 

 Remove the stomach and open it, to find an apparatus 

 for crushing the food. Make a sketch of the digestive 

 system. 



XIV. — Nervous System. Beginning with the posterior- 

 part of the abdomen, carefully remove the body 

 muscles from the abdomen and thorax. Left plainly 

 exposed between the muscles will be found the nerve 

 cord with its branches. Follow that forward to the 

 head. In the thorax it enters a hardened passage, 

 to remove which will require some care. Just posterior 

 to the oesophagus, find a large ganglion into which the 

 nerve passes. Find a similar ganglion in front of 

 the oesophagus. You may be able to see how these 

 are connected by the nerve cord passing around the 

 oesophagus. 



