INFUSOBIA. 411 



rities of interest. The cilia are more developed, and can 

 be more distinctly seen than in either Cothurnia or 

 Vorticella, forming, when in swift action, 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 presume, of a 

 momentary slackening in the speed of the wave. The 

 act of self-division takes place in this animal, as in the 

 Vorticella ; and it is curious to see two Vaginicolce, exactly 

 alike, lovingly inhabiting the same cell. One of the cells 

 which we are now examining is in this doubly-tenanted 

 condition. 



I will now exhibit to you some examples of the most 

 highly organised 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 performed by means of special 

 limbs. These creatures are very common, both in fresh 

 and sea-water, wherever vegetable matter is in process of 

 decomposition ; and hence their presence can at all times 

 be commanded 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 as I 

 believe, to the species S. pustulata. It presents the form 

 of an oval disk, which, when seen sidewise, is found to be 

 flat beneath and convex above. It commonly swims with 

 the belly upwards, and, when exhibited on the stage of the 

 microscope, in almost every case, this surface is pre- 

 sented to the eye. It darts about very irregularly, with a 

 bobbing motion, rarely going far in one direction, but 

 shooting a little distance, and then instantly receding, 

 turning short round, and starting hither and thither, so 

 fitfully that it is very difficult to obtain a fair sight of its 

 structure. Its margin, however, is surrounded by short 



