234 



PICTURESQUE SKETCHES 



surface, while they are often crowded together so 

 closely in putrid water, that one cubic inch of water 

 in that state contains more of these animalcules than 

 there are human beings on the globe. They increase, 

 too, so rapidly, that, according to a calculation care- 

 fully made, as many as 800,000,000 may be derived 

 from a single individual in the course of a month 

 in summer. The method of effecting locomotion and 

 obtaining food is not less singular and interesting in 

 these animals than their minute proportions, and is 

 derived from the possession of very numerous fine hair- 



INFUSORIAL ANIMALCULES.* 



like appendages called cilia, by the constant vibration 

 of which a current is produced in the water. 



The shapes of the hard part or skeleton of the 

 animalcules found in the chalk, in flints, and else- 

 where, are many of them extremely curious and 

 beautiful. Some specimens appear to consist of tubes 



* Fig. 84, Gomphonema. Fig. 85, Bacillaria. 

 Fig. 87, Xanthidium. Fig. 88, Gaillionella. 



Fig. 86, Navicula. 



