HOMOLOGIES AMONG CRUSTACEA. 103 
Are there any evidences of segmentation on the 
under side of the thorax ? 
The appendages attached to the abdomen are called 
swimmerets. At the end of the abdomen is the Ze/son, 
which forms with the last pair of swimmerets the tail 
of the shrimp. The large claws used for grasping prey 
Fic. 89.—Ventral View of Crayfish. 
are the first pair of legs. Count the legs and swim- 
merets. In what ways do the swimmerets differ from 
the legs ? 
Are all the legs alike? What differences do you 
observe ? 
In front of the legs are three pairs of foot-jaws used 
for passing food from the large claws to the mouth. 
These are called maxtllipedes. In front of the maxilli- 
pedes are two pairs of maxille. In front of the maxille 
are the mandibles. 
How many pairs of antenne do you find? Are they 
branched ? 
How do the eyes differ from those of a grasshopper ? 
