272 Mr Meyen on the Digestive Organs of the Infusoria. 



But, it will be asked, what are these vesicles and balls of 

 the same diameter, existing in the bodies of the infusoria, and 

 which have been taken for stomachs ? This question I have 

 continued to ask myself, till an attentive and long continued 

 investigation has enlightened me as to their origin. 



The true infusoria are vesicular beings, whose interior is 

 filled with a naucous substance ; the thickness of the membrane 

 forming the vesicle can easily be ascertained in some of these 

 animals, and in many species I have noticed in this membrane 

 an obvious spiral structure, which establishes a complete ana- 

 logy between it and cellular vegetables. In the large infu- 

 soria, a cylindrical canal (the oesophagus) obliquely traverses 

 the membrane which forms the animal. The lower extremity 

 of this canal dilates more or less when the animal has taken 

 food, even till it attain the dimensions of the balls, which are 

 found in the interior of these same infusoria. The inner sur- 

 face of this part of the intestinal canal is provided with ciliae, 

 which turn round not only the alimentary substances, but also 

 foreign bodies, till they have acquired a spherical form. During 

 the formation of this ball the stomach (for it is evident that 

 we must distinguish this organ by that name) has a free com- 

 munication with the cBSophagus, and, by means of the ciliary 

 apparatus found at the exterior, new alimentary substances 

 are introduced into this canal, and pushed as far as the sto- 

 mach ; but I could not satisfy myself whether the cesophagus 

 was likewise beset with ciliae in the part which separates the 

 stomach from the buccal orifice. When the ball has acquired 

 the size of the stomach, it is expelled by its other extremity, 

 and pushed into the cavity of the animal. It then forms a 

 new ball, if any solid substances exist in the sm-rounding 

 liquid. This second ball is itself pushed into the interior of 

 the cavity of the animal, and drives before it the first ball, 

 along with the mucosities between the two ; the successive 

 formation of similar balls by the matter received into the 

 animal, continues in the same manner without interruption. 

 It is the simultaneous existence of many of these balls that 

 made M. Ehrenberg believe that these animals were polygas- 

 tric. If solid substances do not exist in the surrounding liquid, 

 then the balls are less solid, and they appear in the forms 



