CYCLOPS. 145 



(a) Are the eyes stalked or sessile? They frequently show a 

 peculiar reaction to light. If the light is cut off from the micro- 

 scope, the eye will be seen to rotate on its axis. If the light is 

 admitted again, the eye rotates back to its original position. 



(6) The fii'st antennce are very small and project ventrally. 

 What is the chief function of the second antennae? 



(c) Several appendages will be seen inside of the shell, but 

 it is hard to determine their exact relation. The functions of 

 some of them may be apparent. 



A draioing is desirable. 



CYCLOPS. (Water-Flea.) 



Most any free-swimming copepod, either fresh-water or marine, 

 will answer quite as well as the fresh-water Cyclops. 



Cyclops may be found in almost any pool of fresh water and 

 the marine forms are among the most abundant of the animals 

 of the sea. Surface skimming of the sea, made with a net com- 

 posed of cheese-cloth or silk bolting-cloth, will yield an abun- 

 dance of material. 



1. Watch the animals and see how they swim. With a 

 pipet try to catch a certain individual and see whether the jerky 

 movements probably aid these animals in escaping enemies. 

 Determine what organs are used in swimming. 



2. Examine specimens that have been confined under a cover- 

 glass with a microscope, and notice the shape of the body. 

 Into what parts is it divided? Count the number of segments. 

 Look for evidence of fused segments. Notice how the spines on 

 the abdomen are arranged. 



3. Examine the appendages. 



(a) Do you find eyes that are equivalent to the usual arthro- 

 pod eyes? Do you find an e3^e-spot? If such a spot is found, 

 determine its position and shape. 



(h) Which pair of antennce is largest? Why are the large 

 antennce fringed with spines? 



(c) Are there thoracic or abdominal appendages? Are any 

 appendages other than the first antennae used in swimming? 

 10 



