46 STUDIES OF ANIMAL TYPES 



lipeds? Remove the next, or first, maxilliped. Has it a 

 gill? How does it compare in size with the other two? 

 This completes the appendages of the thorax, for the re- 

 maining ones belong to the head. 



The next two pairs of appendages are thin and delicate, 

 and one must hunt for them carefully. They correspond 

 to the lower jaws of the locust, and are given the same 

 name, maxillce. After they have been located and sepa- 

 rated from each other (they lie directly in front of the first 

 pair of maxillipeds), note a sort of curved, spoon-shaped 

 plate on the second maxilla. It moves back and forth in 

 the anterior opening of the gill chamber, and scoops the 

 water out of the chambers, as it were, thus giving oppor- 

 tunity for fresh water to enter from behind. The next pair 

 of appendages is the mandibles. Each is hard, with toothed 

 edges, and 'each has attached to its anterior edge a short, 

 curved appendage, known as the palpus. These should be 

 compared with the mandibles of a locust. 



Now note the next pair of appendages, the two long 

 antenncB. Above each antenna, but beneath the eye, is a 

 flat, bladelike branch of the antenna. It probably pro- 

 tects the eye. Note that the eyes are stalked. Pull out 

 the eye and note the length of the stalk. The stalk can 

 turn the eye so that it can look in any direction. 



Lastly note the pair of small, branched antennae known 

 as the antennules. 



Make a drawing of all the appendages of the right side 

 after having placed them in order. 



Note the great similarity in structure of these organs not- 

 withstanding their diversity of function. 



C. TOPICS FOR FURTHER STUDY. To what branch 

 does the crayfish belong? What other animals belong to 



