116 Cilia r/j Molinns in Ilepfiie.'i and IVarvi-bloodcd Aiihnah. 



Huschke ; and they have more recently (1832) been repeated 

 by John Muller * and RaspaiJ.f Again, I find that some of 

 the facts respecting the moUusca have been noticed in the mus- 

 sel, and two or three other species, by Leeuwenhoek, Baker, 

 Hales, Erman, Treviranus, Gruithuisen, Huschke, Baer, and 

 Raspail. These authors, however, have for the most part ob- 

 served the phenomena but partially, and interpreted them er- 

 roneously, excepting Huschke, if I may judge from the brief 

 reference to his obser\ations on the mussel and salamander, in 

 Burdach's Physiologie + — for I have not seen his original paper § 

 — and Gruithuisen,]) who discovered the cilia and currents in a 

 species of fresh-water snail, and took a correct view of their na- 

 ture and use. Subsequently, observations have been published 

 on the mussel by Carus^ and Guillot,** in 1831, and on the 

 ascidia by Mr Lister.ff The singular rotatory motion of the 

 embryo of mollusca within the egg, described by Swammerdam, 

 Leeuwenhoek, Baker, Baster, Stiebel, Hugi, Carus, and Grant, 

 had also been referred to the same class of phenomena ; and Dr 

 Grant first demonstrated the existence of cilia as the organs by 

 which the motion within the ovum is produced, though he seems 

 not to have been aware of its connexion with the respiratory 

 process. 



Having at the time mentioned ascertained the existence of the 

 motion in the batrachia, the principal tribes of mollusca, the 

 annelida, and the actinia, and knowing that it had been found in 

 infusory aiiimalcules and zoophytes, I stated it as probable, on 

 generalizing the results of the observations, that it prevailed 

 very extensively in the animal kingdom. Accordingly, in pro- 

 secuting tl>e inquiry with this view, when other avocations per- 

 mitted, I have ascertained its existence in several additional in- 

 stances. The account of these I reserve for an article which 

 I have prepared for the Cyclopaedia of Anatomy and Phy- 

 siology, in which I shall endeavour to give a review of the 

 whole subject, and whe.e I hope, at the same time, to be able to 



• Burdach, Physiologie als Erfahrungs-wissenschaft. Band iv. p. 434. 



t Chimie Organique, 1833, p. 250. t Loc. cit. 



§ In the Isis for 1826. f{ Nova Acta Naturae Curioaorum, vol. x. p. 437- 



% Nova Acta Nat. Cur. vol. xvi. 1832. 



•• Journal de Physiologie, tome si. 



ft Phil. Trans. 1834, p. 378. 



