HISTORY. 63 



that Miiller's animalcule is really the ciliated emhryo of Alcyonella. He admits his inability 

 to determine the nature of the brown egg-like bodies found in the interior of the tubes, and 

 denies to them the office of eggs. In a subsequent note by the same author, published in the 

 ' Isis,' 1830,* he ventures the opinion that the Tubularia sultana of Blumenbach is only the 

 Difjlugia proteiformis, a minute Rhizopod now well known, and originally described by 

 M. Leclerc, in a memoir presented nearly forty years previously to the Institut.-j^ 



In a still later memoir,^ ]\Ieyen informs us that Nordmann has seen Crustacea escape from 

 the statoblasts of Akyonella ; and relying on this certainly erroneous observation, he concludes 

 that the statoblasts of Alcyonella and Cristatella are nothing more than parasites peculiar to 

 these genera. 



In 1828, Dr. Fleming published his ' History of British Animals. '§ In this work he 

 enumerates under the genus Plumatella two species, P. repcns and P. gelatinosa, as inhabiting 

 the fresh waters of Scotland. His P. rejjens is undoubtedly the true P. rej)ens, but his P. 

 gelatinosa is Fredericella sultana. Dr. Fleming has traced the entire course of the alimentary 

 canal, and has recognised in these animals the true polyzoal type of structure. 



Ehrenberg, in his ' Symbolee Physicffi,' 1831, defines the genus Alcj/onella,\\ but this 

 definition embraces the different species of Plumatella, as well as a new Polyzoon which he 

 had discovered in the neighbourhood of Berlin, but which he must have observed very imper- 

 fectly, for its structure is so peculiar as to place it even in a family distinct from that of 

 Alcyonella, with which he associates it, under the name of Alcyonella articulata. Gervais, 

 ■who subsequently found it at Plessis-Piquet, near Paris, saw the necessity of characterising it 

 as the type of a new genus, to which he gave the name of Paludicella.^ In 1837, Mr. 

 William Thompson, of Belfast, discovered this interesting Polyzoon in Lough Erne, in the 

 county of Fermanagh ; and it has since been found in abundance in other localities in the 

 British Islands, and on the Continent. 



At the meeting of the British Association for the Advancement of Science, held at Edin- 

 burgh, in 1834, Sir John Graham Daly ell** describes, under the names of Cristatella mirahUis 

 and C. paludosa, two species of Polyzoa as occurring in the fresh waters of Scotland. His 

 C. mirahilis is undoubtedly the C. mucedo of Cuvier, while his C. paludosa is certainly not a 

 Cristatella at all ; and from the description contained in the report of his paper, it is impos- 

 sible to identify the animal so designated. He gives, on the whole, a very good description 



* MeyeNj Nachtragliclie Bemerkungen zur Natiu'g. der Polypeu des siissen Wassers. ' Isis,' 

 1830. 



t Leclerc, Sur la Difflugia, nouveau genre de Polvpe amorplie. 'Mem. du Museum/ tome ii, 

 p. 474. 



{ Meyen, Beitrage zur Zoologie gesammelt auf eiuer Eeise urn die Erde, p. 180. 'Nov. Act. 

 Nat. Cur.,' 1834. 



& Fleming, ' An History of British Animals, exhibiting tlieir descriptive characters.' Edinburgh, 

 1828. 



II Ehrenberg, ' Symbolfe Physicfe; seu icones et descriptiones animalium,' &c. Berol., 1828 — 

 1831. 



1 Gervais, Recherches sur les Polypes d'eau douce des genres Plumatella, Cristatella, et Paludi- 

 cella. ' Ann. Sci. Nat.,' 2' ser., vii, p. 74. 



** D.iLYELL, On the propagatiou of certain Scottish Zoophytes. 'Rep. Brit. Assoc.,' 1831. 



9 



