no. not. PARASITIC COPEPODS—CALIGIDJE— WILSON. 531 



Gerstaecker published several years later another attempt at the sys- 

 tematization of this group. His classification is based almost entirely 

 upon the structure of tho appendage* and the genital segment, and 

 has remained the accepted classification up to the present time. For 

 the paper published by Bassett-Smith in 1899 can scarcely be called a 

 classification; it is rather an enumeration of species with portions of 

 the synonyms. 



In Gerstaecker's work there are certain errors which can be cor- 

 rected, and additions which must be made in order to bring the group 

 up to date. The latter is especially true of North American genera and 

 species, several of which were omitted by Gerstaecker through lack of 

 identification. 



The name also, Nogagina, which he suggests for his second subfamily, 

 is very unfortunate since the genus called by older zoologists Nbgagus 

 is really made up entirely of the males of other genera. Hence it has 

 no right to be continued at all, much less to be taken as the type of a 

 subfamily. Any attempt to preserve this old genus must be really the 

 introduction of a classification based entirely upon males into the midst 

 of another which considers both sexes equally. 



Furthermore it does not seem that Gerstaecker's arrangement shows 

 as clearly as might be done the gradual transition from non-degenerate 

 forms like Caligus and Lepeophtlieirus through those which show the 

 beginnings of degeneration, like Gloiopotes and Alebion, down to 

 Pandarus and Cecrops which are manifestly quite degenerate. 



The monograph published by J. D. Dana in 1852 on the Crustacea 

 of the Wilkes Exploring Expedition contains the onl} T attempt at a 

 classification of the parasitic copepods thus far made by an American. 

 He divides the group into three tribes according to the structure of 

 the cephalo thorax, the presence of a carapace, and the structure and 

 arrangement of the thoracic legs. He separates the second of these 

 tribes, the Caligoidea, into three families according to the segmenta- 

 tion of the first antenna 1 and the structure of the maxillipeds. The 

 second family, the Caligidae, he subdivides into four subfamilies on 

 tin- structure of the mouth parts and the external egg tubes. 



The classification here presented, like all its predecessors, appro- 

 priates the best iii those which have gone before, especially that of 

 Gerstaecker, adds the new genera and species up to date, and such 

 North American forms as have been omitted. It can not claim origi- 

 nality since it differs chiefly in arrangement, but it is hoped that this 

 change in arrangement will show better than heretofore the relation- 

 ships between the genera. 



