NUTRITION IN THE INFUSORIA. 97 



provided for the digestion of the food which they 

 receive.* But they are not all filled at the 

 same time ; for some continue long in a con- 

 tracted state, so as not to be visible ; while, at 

 another time, they readily admit the coloured 

 food. It is, therefore, only by dint of patient 

 watching that the whole extent of the alimentary 

 tube, and its apparatus of stomachs, can be 

 fully made out. Fig. 2e55, above referred to, 

 exhibits the Leiicophra patula of Ehrenberg,'|" 

 with a few of its stomachs filled with the opaque 

 particles ; but Fig. 256 shows the whole series of 

 organs, as they would appear if they could be 

 taken out of the body, and placed in the same rela- 

 tive situation with the eye of the observer as they 

 are in the first figure. In some species, from 

 one to two hundred of these sacs may be 

 counted, connected with the intestinal tube. 

 Many of the larger species, as the Hydatina 

 senta, exhibit a greater concentration of organs, 

 having only a single oval cavity of considerable 

 size, situated in the fore part of the body. In 

 the Rotifer vulgaris, the alimentary canal is a 

 slender tube, considerably dilated near its termi- 

 nation. In some Vorticellce, the intestine, from 

 which proceed numerous caeca, makes a complete 

 circular turn, ending close to its commencement : 



^ Ehrenberg terms these Polygastric infvsoria, from the 

 Greek, signifying with many stomachs. 

 I Trichoda patula. Muller. 

 VOL. II. H 



