/. CRUSTACEA: COPEPODA. 



421 



or complete, of a circulatory system, and the absence of gills are 

 afl evidences against the view which would consider them primitive. 



Order I. Eucopepoda. 



The forms to which the foregoing description will apply are the Euco- 

 pepoda, and include many species, which often occur in enormous numbers 

 in both fresh and salt water, forming the larger proportion of the plank- 

 ton. They thus furnish the most important food supply not only for fishes 



FlG. 423. 



FIG. 424. 



FIG. 423. Female Lernceocera esocina. (From Lang, after Glaus.) A, armlike proc- 

 esses of anterior end; d, digestive tract; es, egg-sacs; od, oviduct; *i- 4 , rudi- 

 mentary thoracic appendages. 



FlG. 424. Argulus foliaceus. (From Ludwig-Leunis.) a, sting; a', antenna ; b, 

 mouth; c, intestine with liver; d, abdomen; pm 1 , pm s , first and second maxilli- 

 peds ; p l -p*i biramous feet of thorax. 



but for those giants among mammals, the baleen whales. Cetochilus sep- 

 tentrionalis occurs at times in such myriads that the sea for long distances 

 is colored red. 



The CYCLOPID.E, with no heart and paired egg sacs, are fresh-water 

 forms; Cyclops* (fig. 7). CALANID^E, fresh water and marine; heart pres- 

 ent, single egg-sac. Diaptomus,* fresh water (fig. 422); Cetochilus,* Pon- 

 tilla* marine. HARPACTIDJS, creeping forms, mostly marine; Cantho- 

 camptus* fresh water. The CORYC^ID^E, which are half parasitic and 

 include the wonderfully iridescent Sapphirina * (upon pelagic animals, as 



