92 



CTENOPHORA. 



Beroe Forskalii Chun. This species Wagner likewise records to have observed (together 

 with B. cucumis) in the White Sea. His remark that it "hat eine so grosse Verbreitung, dass man sie 

 in alien europaischen Meeren antreffen kann" (Op. cit. p. 54), does certainly not support the belief 

 that his identification of this species was correct, there being no other statements of its occurring in 

 the Atlantic or the European Seas, except the Mediterranean. A support of his statement is, however, 

 found in the fact that Walter") records to have observed two species of Brror at Spitzbergen, one 

 of which must also have been B. Forskalii. if the observation is correct. 



That B. Forskalii really occurs in the Atlantic I cannot doubt. This is also supported by the 

 fact that the collection of the Copenhagen Museum contains a pair of specimens taken at 5" N. 21° W. 

 (Hygom, 1856) and at 47° N 7° 30' W (in the Bay of Biscay, ^g/g. 1861), which I think must be 

 referred to this species. Accordingly I must believe that it will prove to be widely distributed 

 in the warm regions of the Atlantic, and it might then well be carried with the Gulf Stream both 

 to Spitzbergen and the White Sea, like Crshis Veneris. — Its occurrence in the Atlantic is in good 

 accordance with the fact that it is distributed over nearly the whole Indo-Pacific (Moser. Japanische 

 Ctenophoren, p. 26), while its occurrence alone in the Mediterranean, besides the Indo-Pacific, as hitherto 

 supposed, was a zoogeographic riddle. 



Zoogeographical Remarks. 



The geographical distribution of the Ctenophores of the Northern Atlantic has been made the 

 object of a more or less detailed study especially by Chun, Romer, Moser and Damas &: Koe- 

 foed. The views expressed above of the synonymy of such species as Pleurobrac/ua pileus., Boltva 

 jnfundibiiluin and Beroe cucnviis having a rather important bearing upon the value of these forms in 

 the stud)- of zoogeography, it may not be superfluous to give here some remarks on this matter. 



The Ctenophores being absolutely dependent on the currents for their distribution, they are, 

 of course, of no small value for the determination of the extension of the different currents — 

 provided that they occur only in the cold or the warm water, and not in both. In case 

 they are so little affected b)- temperature that they may live both in the arctic and the warm regions 

 of the sea, their occurrence at some place or other can, of course, not be taken as a proof of the 

 extension thither of one or the other stream. This appears exactly to be the case with the 

 species Pleurobrachia pileiis, Bolina iiifttiidibuluiii and Beroe ciuioiiiis. Especially the latter, which is 

 decidedly cosmopolitan in its distribution, cannot be regarded as an especially arctic species, charac- 

 teristic of the arctic regions (Chun), or as "hocharktisch und arktisch mit eurythermer Tendenz" 

 (Romer). This species is, in fact, without value for the discussion of such problems. It cannot even 

 be termed a "boreal" form, as suggested by Damas & Koefoed. The same appears to hold good of 

 Bolina, even if it is not cosmopolitan in its distribution, being hitherto known only from the Atlantic, but 

 from the warm region (probably including the Mediterranean) to the most arctic regions of the Polar Sea. 

 Perhaps the case will prove to be somewhat different with Pleurobrachia pileus. As stated above it 



') A.Walter. Biologische und tiergeographische Ziige aus dem ostspitzbergischeu Eismeere. I. Die Quallen als 

 Stromweiser- Deutsche geographische Blatter. Bremen. 1S90. p. 92. 



