I 2' 



the term is usually understood, are u nioiiuijhyletic grou[j, and ihal the larval tornis of the 

 Ectoprocta receive a reasonable amount of explanation by comparini,^ them with the larvae of 

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

 seriously attempted : nor can I beheve thal it would be successful, particularly if the Phylacto- 

 laemata were taken as the startin^' ])()inl. It must be remembered that the Phylactolaemata are 

 the forms which have most freciuentlv been compared with Phoronis. 



Another fact of which sufficiënt account is not usually taken in comparincr Phoronis 

 with the Polyzoa is the palaeontolooical 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 PJioronis or to Ccphalodisciis or to an\- torm 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. I 7) that Rhabdopletwa is related to the Graptolites. 



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

 ally of Cep/ialodisc7is, the afhnity 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 wa)- 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 Cephalodiscus sibogae. No 

 such specimens were found, but a microscopical e.xamination of the surface of the stone was 

 rewarded b\- the discover)- of a colony of Rhabdoplciira. 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 Rhabdopleura, which is indeed 

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

 Xorwegian coasts, by the labours of Xorm.\n, Allman and G. O. S.\rs, and more recently 

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

 recorded from the coasts of Ireland and Brittany, by Hinxks 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 Rhabdoplciira 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 Xorth -Sea, from Greenland and from Tristan d'Acunha are described as R. normani 

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



l) XoRM.AN, .-\nn. Mag. Nat. Hist. (7) NIÏ, 1903, p. loi n. 



