I 2- 



the term is usually understood, are a monophyletic group, and that the larval forms of the 

 Ectoprocta receive a reasonable amount of explanation by comparing them with the larvae of 

 Entoprocta. The attempt to explain the facts in the converse direction has, I think, never been 

 seriously attempted ; nor can I believe that it would be successful, particularly if the Phylacto- 

 laemata were taken as the starting point. It must be remembered that the Phylactolaemata are 

 the forms which have most frequently been compared with Phoroiiis. 



Another fact of which sufficient account is not usually taken in comparing Phoronis 

 with the Polyzoa is the palaeontological evidence. The Polyzoa are a very ancient group, and 

 the earliest known forms do not appear, so far as can be judged from their calcareous skeletons, 

 to shew any approach to Phoronis or to Cephalodiscus or to any form which might fairly be 

 supposed to have been ancestral to either of these. 



I do not feel myself competent to express any opinion with regard to the view adopted 

 by .ScHEPOTiEFF (04, p. 1 7) that Rhabdopleura is related to the Graptolites. 



In conclusion, I may state my opinion that while Rhabdopleura is the nearest living 

 ally of Cephalodiscus, the affinity of both these genera to the Enteropneusta has been clearly 

 demonstrated. I am inclined to accept the view that they have affinities in the direction of 

 Phoronis, the Chordata and the Echinodermata, and to reject the suggestion that they are in 

 any way related to the Polyzoa. 



XIX. RHABDOPLEURA. 



While this Report was going through the press Professor Weber sent me a stone from 

 Station 204 in the hope that it might bear additional specimens of Cephalodisctts sibogae. No 

 such specimens were found, but a microscopical examination of the surface of the stone was 

 rewarded by the discovery of a colony of Rhabdopleura. Although the specimen is a mere 

 fragment, with its zooids in poor condition, its occurrence in the "Siboga" dredgings is of 

 considerable interest in extending the geographical range of Rhabdoplejira, which is indeed 

 probably world-wide in its distribution. Originally known from deep water off Shetland and the 

 Norwegian coasts, by the labours of Nijrman, Allman and G. O. Sars, and more recently 

 described from one of the same districts by Laxkester and Schepotieff, it has since been 

 recorded from the coasts of Ireland and Brittany, by Hincks and Jullien respectively; from 

 Tristan d'.Acunha in the South Atlantic by Fowler : and from the Azores by Jullien ; while 

 its extreme recorded limits are West Greenland ') and .South Australia (Harmer, 04, p. 23). 



Several species of Rhabdopleura have been described, although in the absence of a 

 comparative study of the genus it is uncertain how far these are really distinct. The specimens 

 from the North Sea, from Greenland and from Tristan d'Acunha are described as R. norma7ii 

 Allman (~ R. mirabilis Sars). Those from Ireland and Brittany are known as R. compacta Hincks ; 



l) N'oKMAN, -Ann. Ma^. Xat. Ilist. (7) -XIi, 1903, p. loi n. 



