INFUSOEIA. 469 



a filmy ring above the margin, along which, as if upon 

 a wheel, one or more dark points are frequently seen 

 to run swiftly round ; the optical expression, as I pre- 

 sume, of a momentary slackening in the speed of the 

 wave. The act of self-division takes place in this 

 animal, as in the Yorticelloe ; and it is curious to see 

 two Vaginicola, exactly alike, lovingly inhabiting the 

 same cell. One of the cells which we are now exam- 

 ining is in this doubly tenanted condition. 



I will now exhibit to you some examples of the 

 most highly organized forms of this class of animals, 

 in which we discern a marked superiority over any 

 that we have yet looked at, and a distinct approach to 

 those animals whose more precise movements are per- 

 formed by means of special limbs. These creatui-es 

 are excessively common, both in fresh and sea water, 

 wherever vegetable matter is in process of decomposi- 

 tion ; and hence their presence can at all times be com- 

 manded by keeping infusions. In this old infusion of 

 sage leaves for instance, they occur in vast multitudes, 

 past all imagination ; as you may see with a lens in 

 this drop. 



This group belongs to the genus Stylonychia, and 

 I believe to the species 8. pustulata. It presents the 

 form of an oval disk, which, when seen sideways, is 

 found to be flat beneath and convex above. It com- 

 monly swims with the belly upwards, and when ex- 

 hibited on the stage of the microscope, in almost every 

 case, this surface is presented to the eye. It darts 

 about very irregularly, with a bobbing motion, rarely 

 going far in one direction, but shooting a little dis- 

 tance, and then instantly receding, turning short round, 

 and starting hither and thither, so fitfully that it is very 



