HOMARUS AMERICANUS. 161 



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

 outward and backward. The liver will be seen to be attached 

 to the pyloric end of the stomach (l 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 

 circum-esophageal 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 move- 

 ments of the grinding apparatus. Why does a lobster with 

 chela and six pairs of mouth appendages need a gastric mill? 



5. Between the circum-esophageal connectives medially and 

 the large antennary muscles laterally, note the oval excretory 

 organs, called the green glands. They are covered by a very 

 delicate membrane. Poke a small hole in one of the membranes 

 and with a blowpipe show that it is really a thin bladder. Its 

 opening on the antenna has already been seen. 



6. Remove the dorsal wall of the abdomen and trace the 

 posterior portions of the gonads, liver lobes, and intestine. In 

 the sixth abdominal segment the intestine swells to form the 

 chitin-lined rectum and gives off the blind intestinal ccecum. 



Circulatory and Nervous Systems.^ — Remove the carapace of 

 an injected specimen as before, also the gill-cover and gills on 

 one side. 



1. There can generally be seen, through the transparent 

 body-wall, efferent branchial veins, which return the blood from 

 the gills. These unite into six large ones which open into the 



1 The circulatory system of a fresh specimen may be satisfactorily 

 injected with starch-mass by inserting the needle of a hypodermic syrmge 

 into the pericardium from the posterior margin of the carapace. The 

 operation is easily performed when the distance to the pericardium is 

 understood. The carapace may be cut away and the needle inserted 

 directly into the heart k preferred. 



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