AETHEOPODA. 45 



(1) the maxillipeds, three pairs of finger-like append- 



ages attached just in front of the chelipeds ; (Lift 

 up the large outer third pair to see the first and 

 second pairs.) 



(2) the maxillae, two pairs of very small, thin, plate- 



like appendages attached in front of the maxilli- 

 peds; (They lie against the mandibles.) 



(3) the mandibles, thick hard jaws, one on each side 



of the mouth. 

 a. What is the direction of their movement, sidewise 



or lengthwise the body ? 

 h. Observe a three-jointed finger (palp) on each 



mandible. 



G. The Sense Organs. 



1. The Antennae. (The long "feelers.") 



a. Watch crayfishes which have not been disturbed 



and observe the use and movements of the 



antennse. 

 h. What is their "reach" as compared with the 



other appendages ? 

 c. How are they made more flexible than the other 



appendages ? 



2. The Antennules. (The short "feelers.") 



a. How many pairs of antennules are there ? 



3. The Eyes. 



a. Observe that the eye is mounted on a movable 



stalk. 

 i. Of what advantage is the stalk ? 



c. What protection from injury have the eyes ? 



(Touch them gently.) 



d. The cornea, the outer covering of the .eye. 



Observe the division of the cornea into small 



