OF PARAMECIUM. 165 



mecium, I shall proceed to illustrate its organization, and leave 

 any further comparison with that of Stentor to your own incli- 

 nations. This, I think, will not be found very difficult to make. 

 The mouth (fig. 96, m) of Paramecium opens, as I have said, 

 at the bottom of an excavation on the abdominal side, and from 

 it the broad funnel-shaped throat (m to g") passes into the body 

 toward its left side in a curve which is continuous with the 

 spiral trend of the disc, and terminates in a slightly rounded ex- 

 pansion (g-) half-way between the mouth and the posterior end. 

 At first sight, this is all there seems to be that is definite in 

 character about the digestive system, and what I am about to 

 relate now of my experiments in feeding the animal would 

 appear to confirm this conclusion. Yet, before I get through, I 

 hope to set the matter in a very different light. The intussuscep- 

 tion of food by this infusorian is a remarkable phenomenon in its 

 ordinary course of operations, but it is heightened exceedingly 

 by supplying the creature with some strongly colored substance 

 which is palatable to it. I have used indigo and carmine, both 

 of them substances in a partially decomposed state ; the indigo 

 being the settlings from the maceration of the leaves of the 

 Indigo plant, and the carmine the dried Cochineal insect. I 

 found the indigo to be the more available on account of its 

 dense color. A single drop from a common indigo-bag is suffi- 

 cient to furnish occupation for hundreds of individuals. Where 

 the indigo is collected in little heaps, under the microscope, the 

 Parameciums gather around in swarms; and usually remain so 

 quiet whilst feeding that any single individual may be selected 

 for observation, and kept under the eye for a long time, some- 

 times half an hour. I have represented by arrows the course of 

 the particles of indigo as they are whirled along, by the large 

 vibrating cilia (v) of the edge of the disc, against the vestibule 

 of the mouth. Those which are accepted are passed down the 

 throat, by the action of minute vibratile cilia, until they reach 

 the rounded termination, (#,) and there they are kept in a con- 

 stant state of rapid revolution until a pellet of comparatively 

 considerable size is formed, and enveloped in a sort of jelly, or 



