684 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxv. 



show a regular gradation in length, the proximal ones diminishing and 

 the distal ones increasing, from in front backward. The proximal 

 joints of the posterior pair of legs are usually triangular in shape to 

 fit the sides of the triangular posterior thoracic segment. 



They are also produced posteriorly into lobes more or less boot- 

 shaped, with the toes turned outward. In some species {maetdosus^ 

 v&t'sicolor^ lepidostei\ these lobes are as large as or even larger than 

 the joints themselves. 



In the female all the other basipod joints (except the posterior) are 

 simple and without appendages, but in the male the two posterior 

 pairs of legs in all species, and in some the three posterior pairs, carry 

 accessory sexual organs upon their basipods. These will be described 

 more fully later. The endopodites of the hrst pair of legs are three- 

 jointed, the basal joint including the larger part, while the two 

 terminiil joints are very small and short. The latter do not carry setse 

 like the basal joint, and they terminate in a pair of forceps-like spines. 



The endopods of the second pair of legs are not jointed; those of the 

 third and fourth pairs are jointed once near their center. The exo- 

 pods in all four pairs of legs (<re without joints. Kroyer, Vogt, and 

 Lej^dig were deceived by the swollen bases of the large rowing setae 

 into declaring that both exopods and endopods were many jointed, 

 and this error has been religiously preserved down to the very latest 

 text- books. 



Lang distinctly says that the exopods and endopods in the Argulidse 

 "are long and manj^ jointed."^ Parker and Haswell do not make any 

 statement, but Claus's figure, which they publish, shows many joints. 



This tigui>»> was drawn by Claus to show the development of the 

 testes and the sucking disks on the anterior maxillipeds, and he has 

 slurred over many of the other details. That he did not intend to 

 represent the endopods and exopods as actuallv jointed is abundantly 

 manifest from enlarged detailed drawings of the three posterior legs 

 of the male (the figure in question is also that of a young male), in 

 which they are represented correctly as without joints, save for the 

 single middle joint in the endopod of the two posterior legs. Further- 

 more, he distinctly says, in the text accompanying these figures," that 

 "in the place of numerous joints capalile of independent motion, there 

 are only joint-like breaks or intervals apparent in the hair-like foot 

 branches." 



This is certainly the condition in every American species examined, 

 as is readily proved by reference to the musculature. 



In all the exopods and in the two anterior endopods there is a 

 single un})roken muscle strand running from base to tip. In the two 

 posterior endopods this strand is broken at the central joint, as are the 

 muscles everywhere else at joints in all the appendages (fig. 15). It is 



^Part I, p. 316, English translation. 

 ^Edition of 1875, figs. 44, 45, and text, p. 250. 



