52 GENERAL HISTORY OF 



do by means of the List of Infusoria I have furnished at 

 the end of this part. 



The older naturalists considered these vesicles as the 

 ova ; and Baron Gleichen made many experiments to 

 endeavour to see their expulsion, but without success. 

 This idea of the Baron's respecting the nature of these 

 bodies is the more remarkable, as it is to him we owe the 

 original experiments of feeding animalcules with coloured 

 food; and the fact of these parts becoming immediately 

 coloured, while the surrounding portions remain trans- 

 parent, could scarcely have escaped his notice. 



From the observations of Dr. E., these globular vesi- 

 cles appear to be distinct stomachs, of which a single 

 animalcule belonging to this class possesses many, as 

 noticed in another place. When one of these stomach- 

 cells, or sacs, has been filled with coloured food, and its 

 situation carefully noted, in a short time the coloured spot 

 will have changed its locality, and hence some naturalists 

 will not admit of separate and distinct sacs or cavities, but 

 maintain that the interior of the creature is one large 

 digestive cavity, and that the globular mass of coloured 

 particles has merely changed its position. To this objec- 

 tion, Dr. E. remarks, that he has distinctly observed a 

 sac to fill, and then the particles to pass singly into 

 another, and so on, until the nutritive portions having 

 been imbibed by each cell in succession, the refuse is 

 expelled by the animalcule. That few observers have 

 noticed this process is not remarkable, as it requires sted- 

 fast and incessant observation of a particular animalcule 

 for some time, while a contraction of them, or a turning 

 upon their axis, may mislead, or even a slight pressure or 



