Invertebrate Zoology. 



tion of the cephalothorax. Four well-developed pairs will 

 be found, each consisting of a basal portion and two free 

 terminal blades. The fifth pair are reduced. The mouth 

 parts, consisting of a pair of mandibles and two pairs of 

 maxilla, are too small to be profitably studied at this time. 



Digestive System. Specimens that have been feeding 

 upon some colored substance (carmine) should be selected. 

 They may be rendered inactive by placing a drop of ether 

 in the watch-glass that contains them. The mouth, situate 

 on the lower surface, just behind the origin of the antennae, 

 will be found to lead into a large, somewhat thick-walled 

 crop. From the crop the intestine extends in a direct 

 course to the anus. Does the anus occupy a dorsal or a 

 ventral position? Through which abdominal segment does 

 it open ? 



Circulatory System. Though in certain related forms 

 there is a dorsally situated contractile heart, in the present 

 form, and, indeed, in the greater number of Copepods, 

 rhythmic contractions of the entire alimentary tract produce 

 the circulation of the surrounding coelomic fluid. 



Excretory System. A pair of coiled tubes, the shell- 

 glands, occupy lateral positions in the thorax and open to 

 the exterior through pores at the bases of the maxillipeds. 

 They are only to be seen in specially favorable specimens. 

 The intestine probably has some excretory power, while the 

 entire surface of the body may permit the escape of injurious' 

 gases, combining excretory and respiratory functions. 



The Muscular System is somewhat difficult to demon- 

 strate. It consists of a series of regularly arranged fibres, 



