CHAPTER V. 



THE CRAWFISH. 



1. How many body divisions? The front one 

 is called the head thorax, or cephalothorax. Find 

 a cross groove separating what might be called the 

 head from the thorax. This is called the cervical 

 groove. 



2. Find the pointed projection in front. This is 

 called the rostrum. 



3. The entire covering of the cephalothorax is 

 called the carapace. 



4. How many segments in the abdomen? The 

 middle piece of the tail fin is the telson. Is there any 

 reason for calling it a segment? 



5. To which segment are the side pieces of the 

 tail fin attached? 



6. Separate the third segment of the abdomen 

 from the second and fourth. Remove the interior 

 contents. Examine. The dorsal part of the ring is 

 the tergite. (Compare with the name tergum of the 

 grasshopper.) The ventral part of the ring is the 

 sternite. The side pieces are the pleurites. 



7. The appendages are the swimmerets. Observe 

 that each swimmeret is composed of a main stalk and 

 two branches. 



8. The main stalk is the protopodite. The outer 

 branch is the exopodite. The inner branch is the 

 endopodite. 



9. Do the side pieces of the tail fin have this 

 structure? Are they swimmerets? 



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