104 Dr. Meyen on the Digestive Apparatus of Infusoria. 



inner border of the opposite sale, turns round at the opposite 

 end of the cavity, and is then again for< ed down on the other 

 side; and thus the mass of the globules goes on continually 

 increasing, until again some arc expelled at the anus. The 

 quantity of these globules is sometimes so great that the entire 

 cavity of the animalcule is filled with them, and they lie so 

 near to one another that all of them together form as it were 

 a great ball, which frequently, especially in the Vorticellce, 

 revolves slowly round its centre. This rotatory motion is 

 caused, however, as I have perfectly assured myself, by the 

 force with which the globule newly formed in the stomach is 

 propelled into the cavity, and hits against the under border of 

 the existing ball. In other cases on the contrary, when so 

 many globules are not yet present, this circular rotation is 

 also seen, of which I have already made mention at the com- 

 mencement ; but it has not become clear to me bv what ex- 

 ternal causes this motion is here produced. 



In the true Infusoria, therefore, the substances which they 

 take up are brought in form of globules into the cavity of the 

 body, and here the nutritive substance is extracted from them ; 

 the useless passes off generally in the same globular form in 

 which it entered, but sometimes the intervening slime is reab- 

 sorbed, and the particles of the globule already separate in the 

 interior of the body, which, however, does not frequently hap- 

 pen. 



But what then are those vesicular cavities which occur fre- 

 quently in such great number, and also of very different 

 sizes, in the interior of Infusoria ? Stomachs they certainly 

 are not ; they have nothing to do with the absorbed globules 

 just mentioned, although sometimes those globules penetrate 

 singly into these cavities, which, however, must be re- 

 garded only as an accidental occurrence. The origin of 

 these cavities, as also their sudden and total disappearance in 

 the slimy substance in the interior of the Infusoria, may be 

 observed with the same ease as the formation of the globules ; 

 nay, it is sometimes even possible to observe the formation of 

 such a cavity around one of the absorbed globules, which then 

 after some time again disappears. The microscope shows that 

 these cavities have no distinct membranous sides, but consist 

 in mere excavations of the slimy substance ; they also occur 



