CTENOPHORA. 8l 



sie zerfetzt unci luassenhaft vernichtet; es dauert nach stiirmischen Zeiten oft eine Woche bis man 

 unter dem iiberreichen Material von Bruchstiicken wieder vollig intakte Exemplare entdeckt". Chun 

 then thinks that "ein recht erheblicher Bruchtheil aller Lobaten allein schon durch Wellenschlag der 

 Vernichtung preisgegeben werden, da den Ctenophoren nach den ubereinstimmenden Berichten aller 

 Beobachter ein Regenerationsvermogen abgetrennter Theile durchaus abgeht" (Dissogonie, p. 103). The 

 dissogony is then thought to be a specially acquired means, through which these forms, which are 

 thus far so badly adapted to the life in the surface waters that they are constantly destroyed by 

 the physical environment, secure their survival in this strange struggle for life. 



This supposed inability of regenerating even smaller parts of the body in such fragile and 

 comparatively low organisms appeared to me very strange and not very convincing; I therefore paid 

 special attention to the matter during my stay at the Trondhjem station. I very soon observed spe- 

 cimens which had all appearance of the lobes being in regeneration. Wishing, however, to have the 

 matter put beyond doubt I undertook some experiments in order to have the question solved definitely. 

 Having taken one day a good deal of specimens in a large plankton-net, these specimens, all more 

 or less lacerated through the capture, were put in a large jar, full of water. On examining them two 

 days afterwards I found the wounds closed, and the lost parts (lobes, auricles, tentacles and combs) 

 were very evidently about to regenerate, the vessels of the lobes having already begun to form anew. 

 In the course of a week the specimens had completely regenerated the lost parts, these being only as 

 yet sHghtly smaller than the corresponding normal parts. Also the windings of the lobe vessels had 

 been formed again as normal. 



Having thus ascertained that the Bolina has a ver\- considerable regenerating power, I deter- 

 mined to carry out some more exact experiments and try to decide how far the regenerating power 

 goes. Some specimens were cut in different ways. In one the apical organ was extirpated, another 

 was divided in two halves after the sagittal plane, a third after the transversal plane and a fourth 

 was divided horizontally in two parts. The experiments succeded completely. In the course of a week 

 the two halves of each of the vertically divided animals each regenerated the lacking part, likewise 

 the lower part of the horizontally divided specimen regenerated the lacking upper part; only the 

 upper part of this specimen succumbed before it had regenerated the mouth. In one of the halves of 

 the specimen divided after the sagittal plane the two half lobes coalesced in the wrong way so as to 

 form one sagittal lobe; but it afterwards amended it so as to get normal lobes again. That the extir- 

 pated apical organ very soon regenerated, need scarcely be emphasized, this being indeed a small 

 thing in comparison with what the other specimens performed. But this had the special interest of 

 proving that the apical organ has no influence on the regeneration, (as was, of course, also shown b>- 

 the complete regeneration in the lower part of the horizontally divided specimen). 



The experiments were carried out in the time from the i8th to the 28th of July, when my 

 sojourn in Trondhjem ended. The regenerating halves of the specimens had then not yet fully 

 reached the size of the original halves, but it seemed evident that in the course of a few da>-s more 

 they would have reached quite the normal condition again. — It is worth noticing that the regenerating 

 specimens became considerably reduced in size during the regenerating process. 



It may still be noticed that the above mentioned specimens, which were captured in the 



II 



The Ingolf-Expeditioo. V. J. 



