60 HISTORY. 



marine Polyzoa, and detected the cilia by whose action these currents were produced;* he 

 observed similar currents, and the cilia causing them, in some fresh-water Polyzoa which he 

 found in the Isle of Walcheren. 



We have seen that Trembley ascribed the currents in question to the motion of the tenta- 

 cula, while Rosel, on the other hand, attributed them to the water ejected from the mouth. 

 Leendert Bomme has the credit of referring them to the true cause ; while in this discovery he 

 has effected an important extension of our acquaintance with vibratile cilia, organs which had 

 previously not been known beyond the Infusoria and Itotifera, and which have since been 

 recognised as so very widely distributed, and so intimately connected with some of the most 

 important functions of living beings. 



In the ' Vermium terrestrium et fluviatilium Historia,' published in 1773,f Miiller insti- 

 tutes the name of Tubularia repens for the " Kammpolyp " of Schiiffer, which he considers 

 specifically distinct from the " Federbusch-polyp " of Rosel, chiefly on the grounds of its being 

 deprived of the collar, which, as we have already seen, Rosel has erroneously attributed to his 

 animal. 



Miiller has distinctly traced with Trembley and Baker an oesophagus, stomach, and intes- 

 tines, and has pointed out the error of Rosel regarding the statoblasts, which this naturalist 

 mistook for the seeds of Lemna. 



In September, 1774, Blumenbach described, at a meeting of the Royal Society of Got- 

 tingen, a new fresh-water Polyzoon, which he had discovered in the neighbourhood of that 

 town.^j; He names it Tubularia sultana, and gives a figure of it in his ' Manual of Natural 

 History,' published in 1779.§ It is at once distinguished from all previously described fresh- 

 water Polyzoa by the tentacula being disposed in a circle, instead of presenting the form of a 

 crescent, by which the others are all characterised. Blumenbach's Tubularia sultana is the 

 Polyzoon afterwards discovered by Gervais at Plessis-Piquet, near Paris, and for which 

 this naturalist found it necessary to constitute a new genus under the name of Fredericella. 

 Blumenbach characterises it in his manual as " Tubularia crista infundibuliformi, ad basin 

 ciliata ;" the latter part of this diagnosis can scarcely refer to the true vibratile cilia which clothe 

 the tentacula in their entire length, and is apparently framed from an imperfect observation of 

 the caliciform membrane with which the base of the plume is furnished, and whose deeply 

 festooned margin may have suggested the character " ciliata." 



In 1776, Eichhorn published his ' Beitrage zur Naturgeschichte der Kleinsten Wasser- 

 thiere.'ll In this we have a description with figures of a fresh-water Polyzoon, which he calls 

 " Der Polyp mit deni Feder-busch." Eichhorn's animal would seem to be the attached form of 

 Plumatella repens, and identical with Schaffer's. He represents a specimen extending over 



* Leendert Bomme, ' Bericht aangaande verscheiden zoonderlinge Zee-Insecten.' Acta Vliss., 

 1769. 



t MuLLER, 'Vermium terrestrium et fluviatilium Historia.' Lips., 1773. 



{ Blumenbach, Voii den Federbusch-polypen in den Gottingeschen Gewassern. ' Gottin. Mag.,' 

 i, p. 117. 



^ Blumenbach, ' Handbuch der Naturgeschichte.' Gottingen, 1779. 



II Eichhorn, 'Beitrage zur Naturgeschichte der kleinsten Wasserthiere in den Gewassern und 

 um Danzig.' Danz., 1776. 



