INFTSORIAL ANIMALCULES. 53 



other injury loosening these cells, may occasion a volun- 

 tary change of place. Another objection to their being 

 separate sacs or cells for the purpose of digestion is, that 

 observers have not seen the canal or tube connecting them 

 together ; this Dr. E. admits is the case in many species, 

 owing to its extreme tenuity. Also, that from its peculiar 

 office, namely, the transmission of the food from one cell 

 to another only, like the oesophagus in large animals, the 

 tube possesses a contractile action, so that the difficulty 

 of detection is augmented. Dr. E. affirms he has dis- 

 tinctly seen their canals while the food has been passing 

 from one stomach cell to another ; and in all his works, 

 except Die Infnsionsthierchen, has presented us with draw- 

 ings of them, and the manner in which they connect all 

 the cells together. For observations of this kind, it will 

 be advisable to select a large specimen of either of the 

 following species : — Chilodon cucullulus, Trachelius ovum, 

 Vorticella chlorostigma, or convallaria, Opercularia articu- 

 lata, or Stylonychia mytilus. 



Again, the position of the discharging orifice has assisted 

 in the erroneous supposition of the excluded substance 

 being ova, for this orifice is not situated in any certain 

 relation to the mouth ; for sometimes one orifice is com- 

 mon to both purposes, as in the fresh water Polype, and 

 some other large creatures. In other Polygastrica, it is 

 either situated anteriorly, posteriorly, or laterally, and this 

 again may be either on the superior or inferior side. On 

 this character, Dr. E. has founded the subdivision of the 

 class into famihes, as given in Part II. of this work. 



Anxious to lay before the reader an impartial statement 

 of this question, I shall, before proceeding with any 



