IVORMS, CRAYFISH, CENT IP EDS, ETC. 



149 



The earthworms, leeches, vinegar-eels, hairworms, and 

 trichina belong to the great branch Vermes. 



The crayfish. — The crayfish, or crawfish, is found in 

 most fresh-water ponds and streams of the United States 

 west of Massachusetts. Crayfishes may be taken by a 

 net baited with dead fish, or may be caught in a trap 



Fig. III. — A group of marine worms; at the left a gephyrean, Dendroslonimn 

 cronjhchni, the upper right-hand one a nereid, Nereis sp., the lower 

 right-hand one, Polynoe brevisetosa. (From living specimens in a tide- 

 pool on the Bay of Monterey, California.) 



ip.ade from a box with ends which open in, and baited 

 with dead fish or animal refuse of any sort. They should 

 be brought alive into the schoolroom and kept in a moist 

 chamber. Observe live specimens to see the character- 

 istics of locomotion, and the use of the pincers and the 

 mouth-parts in taking food. 



Kill some specimens with chloroform and study the ex- 

 ternal structure. Note that the body is made up of a 

 series of body-rings or segments (as in the case of insects 

 and worms), which are distinct in the hinder part of the 

 body (abdomen), but are fused in the front forming the 

 cephalothorax. The whole body is covered with a firm, 

 calcareous exoskeleton, which acts as a protective cover- 

 ing for the soft parts within, and also as a firm place for 

 the attachment of the muscles. 



