CTENOPHORA. 



The animals especially preserved by Mr. Ad. Jensen were only 4 in all. Two of these are 

 preserved intact, as type specimens (represented in PI. I. Fig. i), while the two others were sacrificed 

 for anatomical study. Wishing, of course, very much to have some more material, I examined carefully 

 the remains found on the bottom of the tin in which the Umbellula's had been preserved likewise in 

 formaline - - and to my great joy I found therein a good deal of specimens which had dropped from 

 the Umbellulae, among which also some young stages and specimens in different stages of regene- 

 ration. Though, of course, less well preserved than the 4 first specimens having rolled on the bottom 

 of the tin, among a little bottom material from the base of the Umbellulae, during the whole voyage from 

 Greenland to Denmark, - - they were a most welcome addition to my material, without which I would 

 not have been able to work out the anatomy of the animal so completely as has now been the case. 



It was only later on that I came on the thought that possibly still more specimens might be 

 found, if the heads of the Umbellulae were examined. Indeed, I found then in some of the larger 

 ones several specimens of the Tjalfiella among the polyp-bases, and in one case also some specimens 

 a good way out on the polyps. Unfortunately, all these specimens were very badly preserved, being 

 partly more or less compressed between the polypes, partly because the Umbellulae had now been 

 put in alcohol, whereby the Tjalfiellae had been much contracted and quite lost their jelly-like appear- 

 ance. These specimens were then of no use for my studies of the anatomy of the animal; but they 

 gave the interesting information that the Tjalfiella is not bound to the stem of the Umbellula, occur- 

 ring also in the head, among or upon the polypes. 



The question naturally arises here, whether there is possibly a kind of symbiosis between the 

 Tjalfiella and the Umbellula. Though it is, of course, impossible to give a definite answer to this 

 question before direct observations have been made on living material, it may be stated that, so far 

 as evidence goes, there appears to be no direct symbiotic relation between the two animals. One fact 

 seems to me to be especially important for deciding the question of symbiosis, viz. that a specimen of 

 Tjalfiella was found to contain a shrimp in its digestive cavity. This shows that Tjalfiella does not 

 depend on the Umbellula for its food. That those specimens which have taken a seat in the crown 

 of the Umbellula may receive some protection thereby is quite possible (and that Tjalfiella is exposed 

 to attacks from other organisms is clear enough from the facts set forth below, in the chapter on 

 Regeneration) but this will, of course, not hold good for those specimens attached to the stems of the 

 Umbellulae. On the other side it is hard to see how the Umbellula could derive any profit from the 

 presence of the Tjalfiella, even if the latter catches a shrimp now and then. -- The explanation of 

 the occurrence of Tjalfiella on Umbellula most probably is this that on the soft bottom, where Um- 

 bellula occurs, there are so few objects to which the young Tjalfiella can attach itself, the Umbellula 

 offering itself as the best suited for that purpose. If this suggestion be right, one must expect to 

 find it in other localities attached to other objects, living or dead. Further observations are necessary 

 for deciding this question. 



The preservation of the animals in formaline was thus far a fortunate circumstance, as the 

 whole shape and the jellylike consistence of the body was very well preserved. For the study of the 

 histology of the animal this preservation was, of course, not the very best; still it was not the worst 

 either, several minor histological details appearing irreproachably, only the staining being not quite 



