CHAPTER I. 



Infusokia. 



The most minute and the most simple of all living beings, 

 so far as the powers of the best microscopes have yet 

 reached, closely resembles such a ciliated cell as we have 

 been describing. It has been called the Twilight Monad 

 (Monas crepusculum) ; so named because it is considered to 

 be, as it were, the unit of existence — the point where the 

 glimmering spark of life first emerges out of the darkness 

 of nonentity. It consists of a tiny speck of pellucid mat- 

 ter, rounded in form, and supposed, from its movements 

 and from analogy, to be furnished with a single cilium, 

 by the lashing action of which it rows itself through the 

 water. No words can convey an adequate idea of the 

 size of an animal so minute as this ; but the imagination 

 may be assisted by supposing a number of them to be 

 arranged side by side in contact with each other, like the 

 beads of a necklace, when twelve thousand of them would 

 go comfortably within the length of a single inch.* Eight 



* An esteemed lecturer is reported to have lately said that the cheese-mite 

 is an animal of middling size in existence ; in other words, that there are 

 creatures as much smaller than it as there are larger. This is not strictly- 

 correct. The largest animal known is the Borqual {Balcmoptera hoops), which 



