ABT. 5. NORTH AMERICAN PARASITIC COPEPODS WILSON. 15 



In connection with the various appendages it may be noted that 

 their musculature varies according to their importance and function. 

 For the first antennae there are only a few weak muscles, except in 

 Eudactylina^ where the basal joints are prehensile and need strong 

 muscles. The second antennae are supplied with powerful muscles ; 

 in addition to the long dorsal ones already mentioned there are 

 smaller ones on the ventral surface of the head and others within 

 the joints; those which flex the claw of the chela are especially well 

 developed. In Ergasilina, Kr0yeria^ and Congericola the muscula- 

 ture of the second antennae is even better developed than in Dicheles- 



tMum. 



For the mouth tube there is a pair of flexors and a pair of exten.- 



sors, both originating on the ventral surface of the head. The 



muscles connected with the mandibles are weak; in Lernanthro'pus 



Heider considered it more or less doubtful if there was any muscle 



running to the mandibles. There are none connected with the first 



maxillae in any of the species examined by the present author and 



none have been mentioned by any investigator. In connection with 



the second maxillae in Dichelesthium there are three pairs of muscle 



bands, originating on the dorsal surface and running to the basal 



joint of the appendages. One of each pair originates outside and 



the other inside of the long muscle going to the second antennae. 



In Kr0yeria^ Nemesis^ and Donusa the second maxillae are well 



developed and demand a good muscle supply. 



The maxillipeds in all the genera are powerful prehensile organs 

 but they are exceptionally developed in Eudactylina^ Ne^nesis, 

 LevTianthropus^ and C'yhicola. In the two former they are true 

 chelae and in the two latter the terminal claw is toothed. The basal 

 joint of these appendages in each of these genera is filled with strong 

 flexors and extensors, which control the movements of the terminal 

 claw or chela. 



The usual muscles are found in connection with the swimming 

 legs in all the genera, but when the legs are reduced to a single 

 ramus, as in DichelestMurti, Pseudoclavella^ and Ergasilina^ or to 

 mere papillae bearing setae, as in Pseudocycjius and Cyhicola, or 

 wholly disappear, as in Hatschekia^ Caetrodes^ and Norion^ we find 

 a corresponding reduction or disappearance in the musculature. 

 Those genera like LevTianthro'pus^ Anthosovia, and SaguTTi, in which 

 the swimming legs have been transformed into laminae, show con- 

 siderable musculature. In Lemanthropus gisleri^ for example, the 

 first pair of laminae (third legs) show finely branched muscles 

 whose fibers form a definite network over the entire lamina. In other 

 species also the muscles oi ten run to the very end of the lamina. 



In connection with the rectum most genera show the dilator 

 muscles which serve in rectal respiration. 



