562 



ZOOLOGY 



SECT. 



Some of the pelagic marine Eucopepoda (Fig. 458, 2) are re- 

 markable for their brilliant colours and for the extraordinary 

 development of their setse, especially those of the caudal styles. 



The parasitic Eucopepoda, or Fish-lice, present a very interesting 

 series of modifications, illustrating the degeneration of structure 

 which so often accompanies parasitism. Ergasilus (Fig. 459, 1) 



is found on the gills 

 of the Bass (Morone 

 labrax) ; it is readily 

 recognisable as a 

 Copepod, but the ap- 

 pendages are greatly 

 reduced, the antennae 

 modified into hooks 

 for holding on to the 

 host, and the eyes 

 absent. Anthosoma 

 ('2), found in the 

 mouth of the Por- 

 beagle Shark (Lamna 

 cornubica), has recog- 

 nisable appendages, 

 but the form of the 

 body is much modi- 

 fied by the develop- 

 ment of curious 

 overlapping lobes. 

 Nicothoe (3), found 

 on the gills of the 

 Lobster, has antennas 

 and mouth - parts 

 modified for suction : 

 the abdomen is nor- 

 mal, but the thorax 

 is produced into huge 

 lobes, which give it a 

 curiously deformed 

 appearance. luCJwn- 

 di -acanthus (4), the various species of which are parasites on the gills 

 of Bony Fishes, there is, at the first glance, nothing to suggest that the 

 animal is a Crustacean, except the characteristic copepod egg-sacs : 

 the body is depressed, unsegmented, and produced into crinkled 

 lobes, and it requires careful examination to discover that antennules, 

 hooked antennas (ant.2) used for attachment mandibles, maxillae, 

 and two pairs of legs (f.l, f.2) are present. The male (b) is of 

 higher organisation than the female, but of minute size about ,'._. 

 the length of its mate and is permanently attached to her body, 



FIG. 400. Argulus foliaceus, young male. a\, anteiuuile; 

 0-2, antenna ; ab. abdomen ; bj. b, thoracic feet: d. 

 digestive glands connected with intestine ; kfl, anterior or 

 suctorial feet ; kf2, posterior or leg-like portion of second 

 maxilla; ; pa. paired eye ; r. rostrum ; sd. shell-gland ; St. 

 stylet; ts. testis; ua, median eye. (From Lang's Compara- 

 tive Anatomy.) 



