32 CTENOPHORA. 



plankton-net (on the 13th Jnly), were still alive on the 28th, after having been kept all this time in 

 the same jar, without the water having been changed or aerated. They were certainly in a somewhat 

 poor condition at last, but this was evidently due to the high temperature during the last days; so 

 long as the weather remained cool they were in a perfectly healthy state, and I have not the least 

 doubt that they would have kept so for a long time, had the temperature remained low. My experience 

 thus differs considerably from that of Evans & Ashworth, who state that "of a dozen (specimens 

 of Bolina) brought home alive none survived the night" (Op. cit. p. 310). — The high temperature, of 

 course, also influenced the regenerating specimens; otherwise I suppose the regeneration would have 

 been complete during the ten days. — The food of the animals in the jar, where the water was not 

 changed, appeared to be small Peridinians, which developed in great numbers therein. These speci- 

 mens were often observed standing on their lobes on the bottom of the jar, but that did not seem to 

 have any inconvenience to them, and they easily rose to the surface again. 



Through these experiments it is definitely shown that the Bolina is in possession 

 of quite a marvellous regenerating power, and it ma}- not seem unreasonable to suggest that 

 the same will prove to hold good also for other L,obatse — and upon the whole for the Ctenophora. 

 (Also in Beroe cucti-rnis I have seen distinct traces of regeneration; but experiments were not under- 

 taken with that species). Chun's suggestion that the dissogony serves to counteract the destruction 

 caused by a rough sea accordingly does not hold good. 



It may still be mentioned that Chun's statement of the "iibereinstimmenden Berichten aller 

 Beobachter" that Ctenophores cannot regenerate is not quite, correct either. Mertens (Op. cit. p. 494, 

 527 — 528) describes the regeneration of Mertensia ovuv/ and also of Ccsfiis. While the suggested 

 regeneration of Ceshts is doubtless a mistake of the wellknown fact that small isolated pieces may 

 keep alive for a rather long time, it is not quite sure that it is likewise a mistake with the "Beroe 

 compressa" , since he states expressly to have observed the development of new combs. But in any 

 case the literature is thus not without statements that a regenerating power exists in Ctenophorans. 

 And this is, indeed, not the only statement of that kind. There is found another, much more impor- 

 tant and quite unquestionable statement of extensive regeneration occurring in Ctenophorans, viz. in 

 Chun's own, often quoted work on the dissogony. It is there shown that, when the egg of Bolina has 

 undergone the first cleavage, the two halves of the ^^o, when isolated, each develop to a half lar\a, 

 which is fully capable of living and even develops mature sexual products just as the normal larva; 

 do. The.se half larvtc are stated by Chun (Op. cit. p. 105) to regenerate later the lacking half of 

 the body, so as to become, in all probability, quite normal. This observation is, certainh", in much 

 better accordance with my observations of the excessive regenerating power of the grown Bolina than 

 with the assertion of its total inability of regeneration. 



By the "Ingolf'-Expedition Bolina infnndibuluin was observed on the 6th of July 1895, when at 

 anchor on the "Great Hellefiske Bank" in the Davis Strait, off Holstensborg. Specimens were not pre- 

 served, but that it was really Bolina infiindibnluiu can not be doubted. In the plankton-samples there are 

 several pieces of skin of Ctenophores, which I feel rather convinced are of this species; but, of course, 

 this cannot be fully ascertained, so it seems preferable not to give the station.s. From Iceland (Skutiis- 

 fjord, 15. VI. 1892) there are some specimeu.s, ratlier well preserved (with dilute osmic acid) l)y Mr. 



