400 Mr. H. J. Carter on Peridinium cypripedium. 



that most excellent work to which Prof. Clark alludes, viz. ' Les 

 Etudes sur les Infusoires, &c./ Messrs. Claparede and Lach- 

 mann, been able to contribute as much to the description of 

 their second family of Vorticellina as they wished. 



This has now been added by Prof. Clark himself so completely 

 that henceforth no such confusion can exist. But while Prof. 

 Clark's mistake serves to show how very like Urocentrum Turbo, 

 Ehr. (which I believe to be Prof. Clark's Peridinium cypripedium) 

 is to Peridinium, it also affords me the opportimity of pointing 

 out more strongly than has hitherto been done, the striking 

 resemblance between these two Infusoria, situated on different 

 sides of the line mentioned, which, from a late examination of 

 the former, appears to be desirable. 



Prof. Clark's Peridinium cypripedium, if not identical with 

 Ehrenberg's Urocentrum Turbo, seems to differ from it so slightly 

 that it can hardly be termed another species. 



Of Urocentrum Turbo Claparede states {op. cit. p. 134), among 

 other characters, that the mouth or buccal cavity is spiral, and, 

 on behalf of his lamented coadjutor, the late M. J. Lachmann, 

 that the anal orifice is posterior; while Ehrenberg asserts, on 

 the contrary, that the mouth is "not spiral " (Micrograph. Diet.). 

 Claparede also adds that the setaceous or large ciliary appendage 

 is composed of " long cilia agglomerated into a bundle." 



Urocentrum Turbo has been placed by Ehrenberg among his 

 Vorticellse ; but if the mouth be not spiral, as he has stated, and 

 the anal orifice be posterior, as observed by Lachmann — while 

 Prof. Clark, in his minute examination, although unable to de- 

 termine the position of the latter, mentions nothing spiral about 

 the mouth or buccal cavity, and my own observations are of a 

 like nature — then such testimony is opposed to placing this 

 organism in the position assigned to it by Ehrenberg. 



On this account, probably, the intelligent authors of ' Les 

 Etudes ' have made a separate family for it, under the head of 

 "Urocentrina," which they have placed between their Vorticellina 

 and Oxytrichina, probably also seeing, among other things, that 

 the setaceous or large ciliary appendage, by its brush-like form, 

 allied it more strongly to the Oxytrichina (characterized by 

 large ciliary feet) than to any other family of Infusoria. 



While, then, Urocentrum differs so much from the ciliated 

 animalcules, on the animal side, as to afford the type of a sepa- 

 rate family, it so nearly resembles Peridinium, on the vegetable 

 side, that Pi-of. Clark has set it down as one of the latter — an 

 oversight which needs explanation, lest the organization of Uro- 

 centrum Turbo should be applied to that of the Peridiniens. 



By reference to the 'Annals' (1859, vol. iii. p. 15) it will be 

 observed that I have endeavoured to clear up the confusion which 



