172 ARTHROPODA 



2. The heart extends through the posterior third of the 

 thorax. Remove the upper part of the delicate 'pericardium 

 surrounding it, cut its arterial and other connections, and 

 place it in water. Note the shape, the origin of the arteries, 

 and the three pairs of ostia. Do you understand how the 

 heart receives blood? 



3. Trace the gonads as far as the abdomen, noting the 

 single anastomosis between those of opposite sides just in 

 front of the heart. Beneath the heart the sexual ducts are 

 given off — vasa deferentia in the male, oviducts in the fe- 

 male. Trace one outward and downward to its opening by 

 removing a portion of the body wall and of the basal joint 

 of the proper leg. 



4. Remove the posterior lateral body wall forward to a 

 position opposite the anterior third of the stomach. Pull the 

 anterior lobe of the liver, which extends beneath the stomach, 

 outward and backward. The liver will be seen to be at- 

 tached to the pyloric end of the stomach (i. e., the smaller 

 part, where the stomach passes into the intestine). Cut this 

 attachment and note that it is really where the liver opens 

 into the stomach. Just back of this point the right and left 

 lobes of the liver are connected by a cross branch passing 

 beneath the intestine. Remove one liver lobe back to the 

 abdomen. After having the circumesophageal connectives 

 pointed out, remove the stomach by cutting the esophagus, 

 the intestine, and the bands of muscles attached to the 

 stomach. Examine it in water, noting the cardiac and 

 pyloric parts, the chitinous grinding and straining apparatus 

 in the interior, and the muscles and plates that cause the 

 movements of the grinding apparatus. Why does a lobster 

 with chelae and six pairs of mouth appendages need a gastric 

 mill? 



5. Between the circumesophageal connectives medially 

 and the large antennary muscles laterally, note the oval ex- 

 cretory organs, called the green glands. They are covered 

 by a very delicate membrane. Poke a small hole in one of 



