AMERICAN PARASITIC ARGULID.E— WILSON. 



677 



function with those called similarly maxillipeds in the Caligida\ And 

 since the habits of the two groups are alike we may reasonably assume 

 that these similar appendages would correspond in origin and mor- 

 phological signiticance. 



But Claus has already proved that the so-called maxillipeds in at 

 least a part of the Caligida^ (all the species in which he could prove 

 anything) are the endopodite and exopodite, respectively, of the pos- 

 terior maxilla^. Such being the case, we are compelled to regard these 

 maxillipeds as similar 

 in origin until definite 

 proof can be obtained 

 from their early devel- 

 opment. 



The three regions in 

 an Argulid's body, there- 

 fore, are as we have 

 already named them, a 

 cej}halo-thorai\ in which 

 only the anterior seg- 

 ment of the thorax is 

 united with the head, a 

 free thorax of three well- 

 defined segments, and an 

 ahdom en , unsegme n ted 

 and without appendages. 

 The old name, ''tail," 

 has persistentl V clung to 

 this posterior region, in 

 spite of the fact that it 

 contains the cloacal por- 



FiG. 12.— Dorsal view of adult Argulus megalops female. 



a., JUNCTION OF CEPHALO— AND FREE THORAX; al., AL.E OR 



WINGS OF carapace; a. p., anal papill*; r., cephalic area 



OF carapace; v.. longitudinal CHITIN rods; .S-. ;., SEMEN 

 RECEPTACLES. 



tion of the intestine, to- 

 gether with the testes in 

 the male and the seminal 

 pouches in the female. 



The cephalothorax is 

 much larger than ])oth the other regions, and is developed into a broad 

 horseshoe-shaped shield or carapace. This shield is strongly flattened 

 dorsoventrally, liut remains convex dorsally and concave ventrally 

 like that of the horseshoe crab. Its sides (except in A. elotigatus) are 

 produced posteriorly into two broad, well-rounded lobes, in whose size 

 and posterior reach we may find all gradations from those which 

 barely cover the bases of the second pair of legs {megaloj)!^. funduli., 

 latus) to others which reach back over the entire thorax and abdomen 

 ^purpureiifi), so that the carapace is the only thing visible in a dorsal 

 view (see figs. 2, 12 (text), 24, 65). 



