186 



Transactions of the Society. 



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 Paramsecia 

 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 Paramsecia 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 entirely surrounded by them. The symmetry of 

 the cilia depends much upon the strength of the solution ; if it is too 

 weak, it seems as if the animal had had time to slightly move the 

 cilia, by struggling, as it were, as they appear crossed and 

 crumpled ; but if the solution of tannin happens to have mixed 

 with the water in a better proportion, the cilia are more rapidly 

 developed, and stand out almost parallel, hardly one being seen 

 to overlap another. (See figs. 33 and 34.)* 



Fig. 33. 



ul^\\'li''^'il^"''/'//l ,M I 



^^ 



^ 



Paramcecium after treatment with weak 

 solution of tannin. 



Paramcecium after treatment 

 with a stronger solution. 



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

 the surface of the Paramsecium, 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 Paramseeium is almost 

 instantly rendered motionless, and the cilia appear to be entirely 

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

 tremity. 



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 is, however, 

 entirely disproved by the fact that they are developed, as it were, 

 instantaneously. 



The action of the tannin on the cilia I believe to be analogous 

 to its action on gelatine, rendering them leathery, and consequently 



* In fig. 33 the cilia should appear rather more crossed and crumpled than 

 they arc there shown to be. 



