CTENOPHORA. 



under the name of Tjalfiella' 1 } tristoinn, and of which the full description is included in this report, with 

 the permission of Mr. Ad. S. Jensen and of the Editor of the "Ingolf" Expedition. By this discovery 

 the view of the Ctenophores is upon the whole considerably widened; the Ctenophoran type, hitherto 

 regarded as rather uniform, is now shown to have a very considerable adaptive power. It would be 

 very singular if Tjalfiella should be the only Ctenophore which has adopted a sessile habit, and there 

 may certainly be reason to expect the discovery of new sessile forms. The difficulty of the preser- 

 vation has presumably been a main cause, why such forms have not hitherto been made known - 

 had the Tjalfiella been simply preserved in alcohol, it would also have been impossible to recognise 

 its characters. In any case it should be recommended to look out very carefully for such forms on 

 future occasions. 



The present report is divided into two mains parts, the first containing the full description of 

 Tjalfiella, the second dealing with the pelagic Ctenophores of the North Atlantic. 



i) Tjalfiella from the "Tjalfe", the name of Mr. A. S. Jensen's vessel on his Greenland Expedition. Tjalfe is a 

 renowned figure in Northern Mythology (the companion of the good Thor on his journey to Utgardj. 



* The Ctenophora collected by the "Challenger" have not been made the object of a special report. In the "Summary 

 of Results'* are given some notes on the Ctenophores observed during the Expedition ; most of them are in the form : "recorded 

 in the note-books . . . Cteuophorae'', sometimes the names Cydippe or Pleurobrachia, Eucharis and Beroi ; being named, but always 

 without indication of the species. Such notes are rather useless. Some value might be ascribed to the statement of the 

 occurrence of a species of Eucharis on St. 217 (o 39' S. 138 55' E. zz ,'n 1875; near New-Guinea), as it may be suggested to 

 have been the Eucharis grandiformis described by A. Agassiz and A. G. Mayer (Acalephse from the Fiji Islands. Bull. Mus. 

 Comp. Zool. 32. 1899), the only species of this genus hitherto known from the Pacific if the identification of the genus 

 has been correct, of which there is, however, no guarantee. Also the observation, at Stat. 165 A (364i'S. 158 29' E. ; between 

 Australia and New Zealand) of "a very long, ribbon-like, animal of a golden green colour, supposed to be a Cesium" (Sum- 

 mary of Results. I. p. 587) is worth recalling, even if it is scarcely at the present moment possible to state which species of 

 Ccstus has been observed here. 



Considerably more interest, however, may be attached to another observation recorded in the ''Summary of Results". 

 On p. 850 is mentioned from St. 217 "Dendrocaelous Planarians, with digitiform processes", and in the most interesting record 

 by Moseley on a large line of driftwood observed near New Guinea (Stat. 217) is mentioned among a number of other 

 animals here observed "a small Dendrocalous Planarian with central mouth, diffuse ovaries, a superior penis, and single 

 generative aperture (which) was in swarms upon everything, not only upon the dead matter, but all over the living crabs' 1 . 

 There is in this description especially one thing, which indicates that this has not been a Planarian, viz. the "superior" penis, 

 supposing "superior" to mean dorsal. I cannot but suggest that this supposed Planarian has really been Coeloplana : the 

 "superior penis" would then evidently have been one of the tentacles. 



On my asking Sir John Murray, whether it might be possible to get some specimens of these Planarians for 

 examination, he kindly applied to the British Museum about the matter, and I had the pleasure to receive some specimens 

 found among Crustaceans from that station. The examination of these specimens certainly left no doubt that they were really 

 Planarians. The matter is, however, not definitely settled thereb3'. The specimens examined had no tentacles or processes, 

 so that they could not have been described as having "digitiform processes" or a "superior penis". It seems then not un- 

 reasonable to suppose that there have really been some Coeloplana among the Planarians, which have, however, become lost 

 on account of the difficulty of preservation. 



It is, of course, impossible now to state anything definitely about this matter, but it will probably be conceded 

 that there are here some points which seem to indicate that Moseley was really the first to observe Coelopiana, though 

 without observing its Ctenophoran nature. 



