620 



the basis of the structure of the first antennae, the Amphaskandria, 

 the Isokerandria, and the Heterarthrandria. Each of these 

 tribes is then divided into its various families upon the basis of the 

 family diagnoses, the families of S ars corresponding in general to the 

 sub-families recognized by Giesbrecht. 



The sub-group Harpacticoida contains two tribes, the Achirota 

 and the Cliirognatha, distinguished according to the structure of the 

 mouth-i^arts with special reference to the maxillipeds. The second tribe is 

 then separated, according to the structure of the first swimming legs, into 

 two sub-tribes, the Pleopoda and Dactylopoda. This is as far as the 

 work has progressed at the present time, and it would be discourteous 

 to try here to carry it any farther. One or two suggestions , however, 

 will be entirely in place. 



It is understood that the Ergasilidae are to be included in the 

 Cyclopoida along with the Lichomolgidae and Corycaeidae, but that 

 the Chondracanthidae are in the last group, the Lernaeoidae. We have 

 already pointed out the close relationship of these four families, which 

 form a natural series from a free-swimming condition as showai in some 

 of the Lichomolgidae, through the various stages of commensalism and 

 semiparasitism seen in other Lichomolgidae and in the Corycaeidae, to 

 the complete parasitism of the Ergasilidae, and the modification and 

 degeneration shown in the Chondracanthidae. 



No longer can there be any objection to placing the Chondracan- 

 thidae in the third sub-group provided their relationship warrants it, 

 and it would seem better to keep the four families together. 



Again further study is likely to emphasize the fact that the Lernae- 

 idae, in spite of their degeneration, are more closely related to the 

 Caligidae and Dichelestiidae than they are to the Lernaeopodidae. 

 Here again as Gerstaecker pointed out in his phylogenetic table, we 

 have a gradation in parasitism, from Caligidae w^hich can still swim and 

 move about freely {Caligus, Lepeophtheiriis ^ Trebius) through various 

 degrees of attachment to their host, with a corresponding loss of the 

 ability to move about [Pandarus , Cecrops and Laemargiis among the 

 Caligidae and all of the Dichelestiidae) to the complete fixity and 

 degeneration of the Lernaeidae. 



This relationship can w^ell be shown by transferring the Lernaeidae 

 to the Caligoida. There will still be left for the last and most degenerate 

 sub-group an abundance of material. 



