HISTORY. 61 



an aquatic stem, and gives a tolerably good view of the expanded plume. He describes and 

 figures the tentacular cilia. He tells us that each tentacle is furnished on the extremity with 

 a depression, which he compares to the nail of the finger. This, however, is evidently the 

 result of an erroneous interpretation of the appearance presented when the curved extremity 

 of the tentacle is turned towards the eye of the observer and fore-shortened. So impressed, 

 however, is he with the resemblance of the tentacle to a finger, that he says the animal 

 may be called " Das Finger-thier," and he is in great delight at seeing one of the sup- 

 posed fingers when separated from the plume swimming about with an apparently spontaneous 

 motion. 



Dumortier andVan Beneden inform us* that Schmiedel, in his 'Icones plantarum,' describes 

 and figures, under the name of Sporigia lacustris, the Alcj/onclla in the condition in which it 

 is found in the autumn after the soft parts have disappeared. The ' Icones plantarum ' was 

 published in 1782. I have not succeeded in procuring it. 



In 1786, was published the ' Animalcula Infusoria 'f of Miiller. In this work is 

 described, under the name of Leucophra heterocUta, a minute animal of whose identity with 

 the ciliated embryo of Alcyonella fungosa, as subsequently pointed out by Meyen, or more 

 probably with that of Plumatella rcjpens, there can be now no doubt. Milller's description is 

 accompanied by figures, very good considering the imperfect construction of the microscopes 

 then available. 



In 1789, we find Bruguiere, in the ' Encyclopedie Methodique,' describing, under the 

 name of Alcyonium fluviatile, a production sent to him by M. Dantic, who found it in the 

 waters of the fountain of Bagnolet, near Paris.J Bruguiere was evidently unacquainted with 

 the memoir of Pallas, but his account leaves us in no doubt of the identity of his Alqjonhtm 

 fl%iviatiJe with the Tubvlaria fiiiNjom of this naturalist. His figure, however, is singularly 

 incorrect ; he represents the animal with a variable number of attenuated filiform tentacula, 

 each terminated by a spherical capitulum, and the whole springing from about seven eighths 

 of the circumference of a circular disc. In his location of the Polyzoon among the Alcyoniu7tis, 

 he errs too, as much as Pallas did when he made it a species of Tuhularia. 



In 1797, Lichtenstein, believing that he had witnessed certain Polyzoa escaping from the 

 little spherical capsules which occur imbedded in the base of SpoiiffiUa, maintained, in a com- 

 munication to the Natural History Society of Copenhagen, that the fresh-water sponge con- 

 sisted only of the cells of these Polyzoa after having been abandoned by the polypidcs ;§ an 

 opinion which could only have arisen from some very confused observations, and probably 

 from his having mistaken a dead Alcyonella for a Spongilla. He further maintains that 

 all the forms of fresh-water Polyzoa then known are only variations of one and the same 

 species. 



Hitherto, no step of importance had been made towards the scientific classification of the 

 fresh-water Polyzoa. The invention by Liunasus of a binary nomenclature, had, it is true, 



* Dumortier et Van Beneden, Hist. Nat. des Polypes Comp. d'eau douce. ' Nouveaux Me- 

 moires de I'Acad.-Roy. de Biuxelles,' tome xvi, 1843. 



•)• Otho Fridebicus MiiLLER, ' Animalcula Infusoria Fluviatilia et Marina.' Hauniae, 1786. 



X Bruguiere, ' Encycl. Method.' Vers, p. 24. 



§ Lichtenstein, ' Skrivter of Naturliistorie Selkabet,' p. 104. Kiobenliavn, 1797. 



