MICROSCOPIC ANIMALCULES. 47 



of life. A drop of water, it is said, may con- 

 tain 500 millions of a certain kind. They are 

 of various colours. They multiply themselves 

 by buds, or by spontaneous division sometimes 

 in the length, and sometimes in the breadth. 

 Sometimes one parent is seen to contain many 

 offspring, and the offspring often passes into a 

 separate state of existence through the shell, or 

 covering of its parent ! 



3. To one singular feature in the history of 

 the Polygastrica we must still more particularly 

 refer. They have apparently no articulated 

 limbs, yet by means of cilia (eye-lashes or fila- 

 ments, resembling very small hairs), some of 

 which are only 13 ^ 00 th of an inch in length, 

 they can move with a velocity which the eye 

 can scarcely follow ; ay, perform feats which 

 the most famous performer at Astley's might 

 well admire, but would hardly venture to imi- 

 tate ; walking, running, jumping, wrestling, 

 flying, swimming, creeping ; so that there is no 

 kind of animal movement which they do not oc- 

 casionally exhibit. Their gymnastics are truly 

 extraordinary I One part of the frame, of some 

 of them at least, the cilia, has attained what 



