LOBSTEH OE CBAYFISH 159 



lying in the cephalothorax have been examined 

 and removed) ; the other, the inferior abdomi- 

 nal artery, runs backward. "What is the relation 

 of the latter to the ventral nerve-chain ? 

 Make an outline dravring of the body of the animal 



seen in vertical longitudinal section, and indicate the 



course of the blood-vessels examined. 



h. The microscopic examination of the blood. — 



Kill a specimen, make an opening through the 

 shell into the pericardium, put on a slide a drop 

 of the fluid which escapes, and examine. What is 

 the color of the blood ? Does it coagulate readily ? 

 What sort of corpuscles does it contain ? Draw. 



D. — The Digestive SysteTn. 



Eemove all of the gills, glands, etc., on one side of the 

 thoracic region so as to give a side-view of 



a. The stomach (lying immediately in front of the 

 heart). — What is the shape of its upper surface ? 

 Notice the muscle bands running in various direc- 

 tions. Endeavor to make out a pair, the ante- 

 rior gastric muscles, passing from the anterior 

 end of the roof of the stomach to the base, the 

 procephaUc process, of the rostrum. What 

 motion do these muscles produce ? Another 

 pair, the posterior gastric muscles, pass from 

 the roof of the posterior end of the stomach to 

 the carapace and end just in front of the cervical 

 groove. Draw the upper surface, showing the 

 attachments of these muscles. Another large 

 sheet of muscle fibres, the great constrictor, 

 surrounds the posterior end on the ventral side. 

 Notice that some portions of the wall of the 



