36 CRUSTACEA 



2. The Abdomen. 



(1) Shape? 



(2) Number of segments? 



(3) Number of appendages (swimmerets) ? 



(4) The telson, last segment, has no appendages. 



(5) The Swimmerets. 



(a) Remxove and sketch the pair from the third abdom- 



inal segment. Note that it has a main stalk and 

 two branches. 



(b) Compare it with the first pair, noting similarities 



and differences, or sketch both to show comparison. 



(c) Compare with second pair. 



(d) Compare with fourth pair. 



(e) Compare with fifth pair. 



(f) Compare with sixth pair. 



(g) Use of the swimmerets? 



(h) Compare with thoracic legs, 

 (i) Compare with maxillipeds. 

 (i) Compare with maxillse. 

 (k) Compare with mandibles. 

 (1) Compare with antennae . 

 (m) Compare with antennules. 

 (n) Compare with eyes. 



(o) Conclusion. — Appendages of the same essential plan 

 or not? 



B. Internal Morphology 



Follow the same plan for dissection as in insect studies. 

 Chloroform a fresh specimen or kill it by warm water, as directed 

 for the clam. 



1. The Circulatory System. Carefully remove, wdth scissors 

 and forceps, the dorsal portion of the abdomen and about one- 

 half inch of the carapace, and expose the heart, which is a whit- 

 ish, oblong organ. 



(1) Pericardial cavity in which the heart is located. Use? 



(2) The heart. 



(a) Shape? 



(b) Size? 



