NO. 1302. AMERTCAX PARASITIC ARGULID.E— WILSON. 683 



The second maxillipecl.s retain more of their original shape. They 

 consist of a short basal segment and four longer terminal ones. 

 The ventral surface of all these segments, over the whole or a part 

 of its area, is raised up into rough papillse, or armed with spines and 

 bristles pointing backward. 



In addition the basal segment has on its ventral surface a raised 

 area, often armed witb spines or bristles. This area projects poste- 

 riorly beyond the border of the joint, and in all species examined 

 except one {hit us) is produced into three strong teeth. For this rea- 

 son it was designated by Kroyer as the "• kammen " (pecten or comb). 

 In many species {lepidostei^ etc.) these teeth are long and very sharp, 

 while in others they take on more of the nature of plates, being broad 

 and squarely truncated or only a trifle rounded posteriorly {laticauda^ 

 catodoiiiJ). The terminal segments of these appendages are armed 

 with two claws and a third process or papilla, often ending in a spine. 

 (Plates X, XII, XXL) 



With reference to the use of these appendages, it is at once evident 

 from the spines, teeth, and rough areas on their ventral surfaces that 

 they serve to keep the Argulus from slipping backward on its host, 

 and that this must be their chief function. 



Such an interpretation is strengthened by the fact that in those 

 species which have the spines and hooks of the antenna? and the ven- 

 tral surface of the carapace particularly well developed {mtfcrdosKS, 

 americanus, etc.) the posterior maxillipeds are comparatively small 

 and poorly armed. 



On the contrary, species like catostomlsindi alosse, where the spines on 

 the antennfe are weak and insignificant, the posterior m^illipeds are 

 large, stout, and well armed. There is thus in every species examined 

 quite a uniform balance between the size and armature of these pos- 

 terior maxillipeds and that of the antennae and carapace. 



That these appendages may also be used for "cleaning the sucking 

 cups and for removing extraneous particles from the cavity," as main- 

 tained by Vogt (184:5), seems very likely from the forceps nature of 

 the claws on the terminal joint, but the present author has never had 

 the good fortune to actually witness such an operation. That they 

 "serve principally as organs of locomotion and may therefore be 

 called creeping feet {j^edes gessorii)^ as the}^ have, indeed, been named 

 l)y Kroyer" (Thorell), does not seem probable either from their struc- 

 ture or their development. And in the scores of living Arguli which 

 have been carefully watched no such use of these appendages has ever 

 been detected. 



The four pairs of thoracic appendages are swimming feet and are 

 the principal organs of locomotion. They each consist of a two-jointed 

 l)asipod and an exopod and endopod, of which the former is slightly 

 the longer. The joints of the basipods on the several pairs of legs 



