18 Mindeskrift for J. Steenstrup. XVI. 



morphosis and the later development of its parasite. Very few indeed — if any at 

 all — of the Parasitic Copepods have been followed up more completely. I therefore 

 feel somewhat abashed in being unable to settle the systematic position of the new 

 genus. I have tried in vain, by going through the vast and dispersed literature con- 

 cerning Parasitic Copepods, to find any close allies to the Chordeuma. None of the 

 established families seem to me fit for its reception; evidently therefore it represents 

 a new family. The obvious idea, that some of the Parasitic Copepods known to infest 

 Echinoderms might be related to the genus in question, I soon abandoned. The 

 ectoparasitic Asterocheridae (10) seem widely different ; the Pionodesmotes phormosomae 

 Bonnier (1, 15), producing galls inside the shell of Phormosoma uranus W, Th., and 

 by its author regarded as the type of a family of its own, does not show any near 

 affmity, and the same is the case with the ^'Philichthys amphiurae''' Hérouard (12), 

 hitherto the only Parasitic Copepod found endoparasitic in any Ophiuroid. Neither 

 seems the structure of Chordeuma to allow an admission into the extremely varied 

 family Ascidicolidae (2, 3, 4, 5 — 8), of which at least one member infests an Echinoderm, 

 the Enterognathus comatulae Giesbr., living in the intestine of Antedon rosaceus (11). 

 Although some of the most degraded members of this family (f. ex. Enterocola, Ente- 

 ropsis, Aplostoma, Ophioseides, Mychophilus) may — the one or the other — show 

 certain features analogous to those found in Chordeuma f. ex. reduction of antennules, 

 reduction or loss of the outer branch of the antenna, of the mandibles or maxillulæ, 

 reduction of the thoracic feet, which may become uniramous, of the abdomen etc, 

 most of these features only occur in the more or less sessile female, while the male 

 is adapted to lead a more or less free life; and all the resemblances are certainly 

 superfieial, only due to convergence, while the fundamental structure as well as the 

 development are very different. 



The fundamental conformity of both sexes in Chordeuma, of the body as well as 

 the appendages — the latter all being uniramous and, except the maxillæ, unsegmented — , 

 the absence in both sexes of every trace of buccal appendages (mandibles, maxillulæ), 

 the blindly closed intestinal tract, without any abdominal part, the absence of eyes 

 in every stage of development, the absence of furcai appendages, and of segmentation 

 of the rami of the swimming feet in the Cyclops-larva etc. are features which, as far 

 as I know, do not occur combined in any other Parasitic Copepod. 



