INFUSORIA. 



containing them be placed between two pieces of glass, they 

 will bo seen swimming about with perfect ease in that little 

 film of liquid, and passing and repassing without even coming 



Fig. !. INFUSORIA. 



into contact. The globules of blood in the human body are 

 variously estimated in regard to size, but when magnified 

 180.000 times do not exhibit an image larger than the ac- 

 companying figure. Many of the infusory animalcules are, 

 however, still more minute, so that 180,000 of them, ^ 

 if formed into a ball and laid upon the paper, would ^ 

 cover even a smaller surface. 



Professor Ehrenberg, of Berlin, has calculated, that 2,000 

 of them placed together would measure but one line, or the 

 twelfth part of an inch. According to this estimate, a single 

 drop of water might contain 500 millions of these minute 

 animals: a number nearly equalling that of the whole human 

 species now existing on the earth! 



But although these animalcules abound in infusions of animal 

 or vegetable matter whence their name infusoria they are 

 not restricted to such situations. They are numerous in all 

 countries, and are found in all waters; not merely in those of 

 the stagnant pool, but in lakes, in rivers, and in the sea itself. 

 From materials furnished to him by the late antarctic expedi- 

 tion, Ehrenberg* has ascertained that they exist even in 

 the ice and snow of the polar sea, and that they are abundant 

 not only in inland seas, and in the vicinity of land, but that 

 the clearest and purest water, taken from the open sea, and 

 far from land, is crowded with microscopic life. These minute 

 organisms have been found living at the depth of 270 fathoms 



Fig. 1. Four common native species, viz. I. Vorticella convallaria . II. 

 Chaetonottti larus. III. Leucophryx spa tufa. IV. Lepadell'i ovalis. 



* Ehrenberg on Microscopic Life in the Ocean at the South Pole, and 

 at considerable depths. Annals Nat. Hist. Sept. 1844. Page 1G9. 



