CTENOPLANA. 723 



of satisfaction. Of the four specimens which I obtained three were mottled with green, 

 the fourth with red pigment; the former were rather larger than the red variety and 

 differed from it somewhat in shape. The red form also differed in minor details from 

 the original tj-pe Gtenoplana kowalevskii Korotneff. Nevertheless, with added experience 

 of specific divergencies, I am now inclined to think that my Ctenoplana rosacea is 

 co-specific with Korotneff 's type, and it seems quite likely that the green form is 

 nothing more than a variety or phase of the same species. 



All the green individuals contained male gonads with their genital ducts, but I 

 was unfortunately unable to satisfy myself concerning the female gonads. It should be 

 noted that great care and the application of very special methods are requisite for the 

 preservation of Ctenoplana. It is well known that some of the Ctenophora dissolve 

 away before one's eyes in certain fluids, and although Ctenoplana does not vanish in 

 this way, the contraction of the tentacular musculature is apt, in healthy specimens, 

 to cause a lamentable shrinkage. 



In his recent account of the Ctenophora' Mr G. C. Bourne places Ctenoplana and 

 the allied genus Coeloplana in a special order of Ctenophora Tentaculata, which he 

 names Platyctenea, at the same time declining " to attach very much importance to 

 the resemblance between Ctenoplana and the Polyclada." Mr Bourne further comes to 

 the conclusion " that the Turbellaria, the Nemertines and the Ctenophora are descended 

 from a common ancestor which is most nearly represented by the larva of Stylochus" 

 [a Polyclade worm]. This is mainly in accordance with the views which I expressed 

 in my paper, and Mr Bourne quotes the Pilidium larva of Nemertines in his 

 comparison, as I also did. Moreover, the term Platyctenea is undoubtedly preferable 

 to the term which I suggested, Archiplanoidea, as an ordinal name, but I am unwilling 

 to refuse any importance to the latter name. I intend it to embody the proposition 

 originally laid down in its main principles by Prof. Chun, that the bilateral Plathelminthes 

 generally have originated from a biradially symmetrical ancestor, and further to express 

 the possibility of the diphyletic origin of triploblastic animals. 



After much labour against the tide we managed to get to a temporary anchorage 

 off the westerly islet of the Conflict Group, intending to make the lagoon before dark, 

 but failing to find the passage we spent a squally night tacking about. Towards the 

 evening a remarkable procession of transparent pelagic animals, Ctenophora of several 

 different kinds, including the ribbon-shaped Gestus, drifted past the islet. These creatures, 

 as I have said, are most difficult to preserve, as they have the peculiar property of 

 undergoing instantaneous disintegration and dissolution .under certain conditions of 

 treatment. 



Next morning I had quite lost my bearings and suddenly found myself heading 

 straight for the reef, but I got the jib and sail down just in time to avoid a collision. 

 It was not until the following sundown that we found the passage and anchored in 

 the lagoon. Just about this time the south-west wind began to blow and I found 

 the lagoon with its loose sandy bottom a most imcomfortable anchorage. In this region 



' A Treatise on Zonlogy, edited by E. Kay Lankester, I'art ii. chap. vii. 190i). The Ctenophora by 

 G. C. Bourne, M.A. 



W. VI. 95 



