8o A GUIDE FOR THE STUDY OF ANIMALS 



5. What limits the range of crayfishes, north and south ? 

 What limits it on land ? What in water ? 



6. When the crayfishes of a given locality are not well 

 adapted to it, what can they do ? 



Suggested drawings. 



a. The whole animal, dorsal surface, preferably without 

 appendages. 



b. One of each pair of appendages, except where they 

 duplicate. 



c. The tail-fin. Label the sixth swimmerets, the sixth 

 and seventh somites. 



d. The gill chamber, with gills in position. Show cir- 

 culation of water by arrows. 



e. A gill, to show construction. 



2. COMPARATIVE STUDY OF CRUSTACEA 



Materials. 



Get together all the different specimens of Crustacea you 

 can collect, and identify the material. Then study each 

 specimen as follows : — 



Questions. 



1. Briefly describe the exoskeleton, if there is one. 



2. What region or regions are clearly segmented .'' 



3. How much of the body is covered by a carapace.' 



4. Has it segmented appendages .■' Classify the append- 

 ages as to their use. 



5. Are the cephalo-thorax and abdomen equally devel- 

 oped .'' If not, which is more developed 1 



6. How many antennae has it } Are the eyes stalked, 

 or are they sessile ? 



7. What organs of respiration has it } Where are they 

 attached .' 



