384 ON THE ACTION OF TANNIN ON INFUSORIA, 



" It may have been noticed, that when these Infusoria have been 

 killed by ordinary means, such as heating the water in which they 

 are contained, the cilia are very difficult to observe, probably 

 owing to their great transparency, so that no correct idea, has, I 

 think, been obtained of their size or quantity. 



" On placing however, a drop of water containing Para?ncecia on 

 a slip side by side with a minute quantity of a solution of tannin 

 and making a junction of the two, it will be seen that the instant 

 the Paramoecia approach the mixed fluids, their motion is arrested, 

 of course in a greater or less degree according to the strength of 

 the tannin. They are generally rendered perfectly quiescent, and 

 the cilia begin to appear and continue to develope until the body 

 of the animalcule appears surrounded by them. The symmetry of 

 the cilia depends much upon the strength of the solution. * * * 



"To bring out the best appearance of the cilia over the whole 

 of the surface of the Parametrium the parabola is required ; the 

 animal then appears as if it were supported on the slip by its 

 cilia. 



" If the tannin solution is strong, the Paramecium is almost 

 instantly rendered motionless, and the cilia appear to be entirely 

 removed, remaining in a more or less confused state at the 

 extremity. 



" I have shown this action to several Microscopists, and so 

 contrary is the remarkable development of the cilia to received 

 ideas, that on nearly every occasion I have been met with the 

 remark that they were not cilia but fungoid growths. This 

 however, is entirely disproved by the fact that they are developed 

 as it were instantaneously." 



Mr. Waddington believes that the action of the tannic acid on 

 the cilia is analogous to its action on gelatine, rendering them 

 leathery. 



Struck with the remarkable appearance shown in Mr. Wadding- 

 ton's illustrations, I made a number of experiments with glycerole 

 of tannin as described by Mr. Waddington. On exposing P. 

 Aurelia to the action of the tannin, I found the effect quite as 

 startling as described ; the animalcules, as the acid began to affect 



