40 Marvels of Pond-Life. 



have always been favourite objects with microscopists. 

 The Germans call them ^' slipper animalcules/^ and 

 they vary in size from 1 — OG"""^ to 1 — 1150"^ They are 

 flat rounded-oblong creatures, with a distinct integu- 

 ment or skin, ^^ through which numerous vibratile cilia 

 pass in regular rows/^f They are furnished with a 

 distinct mouth, and adult specimens exhibit star-shaped 

 contractile vesicles in great perfection. 



The swarm of specimens before us belong to one 

 species, Paramecium aurelia, the Chrysalis animalcule^ 

 and they crowd every portion of the little water-drop 

 we have taken up, and examined with a power of about 

 one hundred linear. When they are sufficiently quiet 

 a power of about four hundred may be used with 

 advantage, and Pritchard recommends adding a little 

 indigo and carmine to the water, in order to see the 

 cilia more clearly, or rather to render their action more 

 plain. The cilia are disposed lengthwise, and Ehrenberg 

 counted in some rows sixty or seventy of them, making 

 an aggregate of three thousand six hundred and forty 

 organs of motion in one small animated speck. This 

 number seems large, but although we have never per- 

 formed the feat of counting them, we should have 

 expected it to prove much greater. Unlike most 

 animalcules they are susceptible of being preserved by 

 drying upon glass, and we su])join a figure from 

 Pritchard, of one thus treated, in which the star-shaped 

 vesicles are clearly seen. These curious organs com- 



* The usual mode of giving dimensions is by fractions thus 

 expressed : 1 — 96" means one ninety-sixth of an inch, 

 f * ]\Iicrographic Dictionary.' 



