78 ZOOLOGICAL EXERCISES. 
12. Masticatory apparatus.—Remove the animal from 
the water and turn it on its back. With a piece of 
blotting paper dry up the water about the mouth. 
With the forceps remove the six pairs of appen- 
dages, and lay them out in order on a glass slide, the 
exterior maxillipedes being nearest you. Compare 
the various parts. The third or external maxillipedes 
have a short broad protopodite (the first joint), from 
from which springs a large and broad endopodite, and 
a narrow exopodite. The endopodite is divided into 
five joints, of which the first two (the second and 
third joints of the maxillipedes) are broad, the last 
three much smaller. The exopodite, or palp, consists 
of a long joint, with a many-jointed appendage. In 
the second maxillipedes the exopodite, or palp, is as 
large as the endopodite. In the first maxillipedes 
the endopodite is short and broad. The second pair 
of maxillz are short and broad ; the first pair are very 
delicate, and not easy to find ina small crab. The 
mandibles are large and strong. 
13. Examine the appendages on the under surface of the 
abdomen. In the male there is one pair only; they 
spring from the first segment and lie longitudinally, 
In the female there are four pairs, each with a 
distinct exopodite, and endopodite. 
