CTENOPHORA. 



S.S 



there were also found some speciiiiens with prohferations from the pharyujj^eal vessels, tliouo^h none 

 had them very richly developed. Being, of course, very anxious to examine specimens from the Med- 

 iterranean, 1 got a couple of large, beautiful specimens from the Zoological Station at Najjles; one 

 of them had the proliferations from the pharyngeal vessels ver\' riclil\- developed, the other had onlv 

 very few proliferations. Later on I got a considerable numljer of specimens from the Mediterranean 

 from the "Thor", and likewise found a very considerable variation in regaril to the proliferations from 

 the pharyngeal vessels; most of them had the proliferations richly developed, but in some of them, 

 among which some of the largest specimens, there were quite few or onlv a single pair of them. 

 Finally I have found the same variations to exist in specimens from the Atlantic. 



The result is then that it is impossible to maintain B. ova fa as a separate species, the only 

 character thought to distinguish it from B. ciicuviis, the proliferations from the pharyngeal vessels, 

 being quite unreliable on account of its great variability. All transitional stages may be found together 

 in the same localitv, in Greenland as well as in the Mediterranean. It is, however, evident that in 

 the specimens from the North European Seas, and probabls' of the whole North Atlantic the general 

 condition is that the pharyngeal vessels have no proliferations, while in the Mediterranean form there 

 is generally a rich development of these proliferations. There may then perhaps be reason to separate 

 the latter as a special form or variety of B. ciicuinis. Also in the specimens from the warm regions of 

 the Atlantic at my disposal I have found the proliferations generally more developed than in the 

 northern form. 



Regarding the synonymy of B. ciicumis I would further point out that it is perhaps not quite 

 certain that Idyia cyathiiia A. Agass. is identical with it and perhaps it is not certain either that 

 Idyiopsis Clarkii L. Agass. is a distinct species as maintained by Moser. As to the first of these, it 

 is true that L. Agassiz states (Op. cit. p. 287) that "there is not the slightest structural difference 

 between the two" (viz. (yaf/i/iia and roseola); but A. Agassiz (North American Acalepha;, p. 39) states 

 that "the ovaries and sijermaries are much longer sacs than in /. roseola, and not so numerous". This 

 character together with the differences in shape ( — "it is widest at two thirds the distance from 

 the mouth; it then tapers as stiddenly for another third of the distance to the mouth, and then very 

 gradually" — ) and habits (— "instead of the sluggish movements which characterize Idyia roseola, 

 Idyia cyathiiia is ver)- active, and seems to retain the embryonic features of the genus, — short rows 

 of flappers, and great activity in its adult condition" — ) would perhaps seem to indicate that it is not 

 identical with B. ciicuinis. 



In the "Japanische Ctenophoren" (p. 20 — 21) Moser reaches the conclusion, after a careful 

 revision of the literature on that subject, that Idyiopsis Clarkii L. Agass. (together with Idyiopsis affinis 

 L. Agass.) should be regarded as a doubtful species; in the "Ctenophoren d. deutschen Stidpolar-Ex- 

 pedition" (p. 157—159) the author maintains it as a distinct species after having examined some well 

 preserved specimens brought home from the Tortugas by Dr. R. Hartmeyer. The characters upon 

 which the species is maintained are: the shape of the body and the position of the costse. Judging 

 from the figures given by Moser the shape is certainly more rounded at the apical pole than is 

 generally the case in B.cucitiiiis — but how much of that is due to contraction on preservation? 

 The polar plates having been withdrawn, it is evident that no small amount of contraction has taken 



