76 A GUIDE FOR THE STUDY OF ANIMALS 



Appendages, paired structures attached to the body. 

 They are named as follows: — 



Eyestalks. (These are not classed as appendages 

 by all students.) 



Antennules, the small feelers. 



Antennce, the large feelers. 



Mandibles, the jaws, one on each side of the mouth. 



Maxillce, the two pairs of small mouth parts just 

 back of the mandibles. 



Maxillipeds, the three pairs of appendages between 

 the maxillae and the large claws. 



Chelipeds, the large claws or pinchers. 



Walking legs, the four pairs of appendages back of 

 the chelipeds. 



Swimmerets, the appendages on the abdomen. 



Openings, five on the ventral surface, as follows : — 



The openings from the excretory organs, through 

 small white cones on the bases of the antennae. 



The mouth, farther back, between the maxillipeds. 



The anal opening, in the last segment of the ab- 

 domen. 



The opening from the reproductive gland, toward 

 the posterior part of the thorax. 



Observations. 



1. How large is your specimen? How does it compare 

 in size with other crayfishes in the laboratory .■' 



2. Describe the shape of the body, contrasting the ante- 

 rior end with the posterior, and the dorsal surface with the 

 ventral. 



3. Study the amount of motion permitted in different 

 parts of the body. What prevents motion .? What per- 



