NOTODELPHYOIDA. 



Remarks. This division comprises a number of Copepoda, which partly 

 differ considerably from each other and according to their organisation, represent 

 several distinct types. Yet, all these forms agree as to habits, in so far that 

 they live as parasites, or more properly as commensales, within Ascidians of 

 different kinds. They were all by earlier authors comprised within a single 

 family, the Ascidicolidce, and this family was by Giesbrecht, together with the 

 Monstrillidce and several other heterogeneous groups, included in the 2nd tribe 

 of his suborder Podoplea, for which the name Ampharthrandria was proposed. 

 I have already mentioned, that the latter name is quite inapplikable for the 

 present group of Copepoda, which comprises both forms with the anterior 

 antennae in the male transformed to prehensile organs, and such in which 

 these antennae are quite alike in the 2 sexes. According to the classification 

 proposed by Giesbrecht, these latter forms should of course be trans- 

 ferred to his 1st tribe, the Isokerandria; but such a transfer appears quite 

 unreasonable, since there are forms, otherwise closely related and even referred 

 to one and the same genus, in which the above-named difference, as to the 

 structure of the anterior antennae, is found. Thus in the male of Doropygus 

 longicauda Aurivillius, as will be shown farther on, these antennae are very 

 distinctly hinged, whereas in the other species referred to that genus they are 

 quite alike in the 2 sexes. It is thereby clearly proved that the above-named 

 character, upon which Giesbrecht laid so much stress, is of far inferior systematic 

 value than opined by that author, and that it in reality must be considered 

 unserviseable as the basis for a more geneial classification of the Copepoda. 

 There are many other much more important diversities to be found on a 

 comparison of the several forms comprised within the present group, and 

 these diversities are in fact of such an essential quality as to make it inad- 

 missible to include all these forms within a single family. This was also 

 recognised by Thorell, who referred the forms observed by him to 3 different 

 families, viz., Notodelphyidce, Ascidicolidce and Buproridcc. The 1st of these 

 families has subsequently been subdivided by Prof. Brady into 2 nearly-allied 



