Prof. R. Jones on the Digestive Apparatus of Infusoria. 105 



generally near the inner surface of the membrane which forms 

 the coating of the animalcule, and at times some of them in- 

 crease to a very considerable circumference, so that the cavity 

 of such a bladder constitutes one-third and one-half of tlie ca- 

 vity of the entire animalcule. That these cavities contain a 

 thin and aqueous fluid and are not filled with air is shown by 

 the remarkably small refraction of rays at their borders, and 

 in the larger Infusoria it may be quite distinctly seen that 

 they do not open exteriorly. Similar cavities are also formed 

 in the mucus of the cells of plants, especially frequent in Hy- 

 pJiomycetes growing in water. 



My botanical researches prevent my working out this sub- 

 ject more fully ; these brief notices may, however, suffice to 

 induce a greater number of naturalists to follow up the ob- 

 servations, which it is true require great patience ; for the 

 above-mentioned facts are not to be seen immediately in every 

 animalcule ; but they are sufficiently important, for already 

 have the Polygastrica passed into all recent works on zoology. 



Prof. Rymer Jones on the Digestive Apparatus of Infusoria^, 



However imposing, from their completeness, the views of 

 Ehrenberg concerning the digestive system of the Polygastrica 

 may be, and sanctioned as they are by almost general consent, 

 we cannot pass over a subject of so much importance without 

 expressing ourselves as being far from admitting their accuracy 

 in all respects, and we must say that our own observations 

 upon the structure of the Polygastrica have led us to very dif- 

 ferent conclusions. 



The positions of the mouth and anal aperture we are well 

 assured, by frequent examination, to be such as are indicated 

 by the illustrious Professor of Berlin ; but with regard to the 

 tube named by him intestine, and the stomachs appended 

 thereto, our most patient and long-continued efforts have 

 failed to detect the arrangement depicted in his drawings. In 

 the first place, as regards the function of the sacculi, which he 

 looks upon as the organs in which digestion is accomplished ; 



* Extracted from Prof. Rymer Jones's work entitled ' A General Outline 

 of the Animal Kingdom.' 



Ann. Nat. Hist. Vol.3. No, 15. April 1839. i 



