396 



INVERTEBRATE MORPHOLO&T. 



1. Suborder Eucopepoda. 



Tliis suborder includes the majority of the Copepoda, and 

 its members are characterized by having only the first thoracic 

 segment fused with the head and by possessing usually a 

 well-developed abdomen. Many are free-swimming, some in- 

 habiting fresh water, as Cyclops and OantJiocamptus, while 

 others are more especially marine, such as Harpacticus, Calanvs 



imx' 



FiQ. m.—A, Philiehihys xiphim seen prom the Dorsal Sxjkface (after 

 Glaus); B, AcMlieres percarum (fiom Bronn). 



(Fig. 177), and Cetochilus, the latter sometimes occurring in 

 enormous schools, and forming an important food-supply for 

 fish and the baleen whales. Some, on the other hand, lead a 

 commensalistic life, occurring in the branchial chamber of 

 Tunicates, e.g. Notodelphys, while a large number of forms are 

 parasitic. The degree of parasitism varies greatly in different 

 forms ; thus many are capable of free existence, becoming 

 parasitic only occasionally, such as Coryccetis and the brilliantly- 

 colored Sapphirina, while others, such as Ergasilus, parasitic 

 on the gills of fishes, and Galigus and Pandarus, though essen- 



