INFUSORIA. 



219 



corals of the Silurian period do not all belong to the lowest 

 forms, but, on the contrary, that many of them have the 

 Bryozoan type of structure ; a fact which we shall hereafter 

 connect with others of a like character, derived from an 

 investigation of the higher classes of the animal series. The 

 subjoined figures (152 and 153) of a beautiful Anthozoan 

 coral (Liiharcea Websteri), from the tertiary sands of Brack- 

 lesham Bay, may be regarded as typical of the polypifera. 



IKFUSOBIA. The waters of every pond and rivulet, of every 

 lake and river, together with those of the great ocean itself, 

 swarm with innumerable minute forms of animal life, which, 

 from the circumstance of their abounding in infusions of 

 vegetable substances, have 

 been called Infusoria. Many 

 of these microscopic organ- 

 isms, like the Monas crepus- 

 culus, measure only about the 

 thirty-two thousandth part of 

 an inch in length, and all are 

 so minute that it requires the 

 highest powers and the best 

 object-glassesofthemicroscope 

 to study their organisation 

 and watch their habits. 



Professor Ehrenberg, the 

 great historiographer of this 

 class, has made some interest- 

 ing calculations on the mi- 

 nuteness of some Infusoria. He ascertained by the micro- 

 meter that two thousand of these organisms, placed together, 

 would measure about one line,* which would give twenty- 

 four thousand in an inch. 



In some infusions, certain species are crowded so closely 

 together, that he estimated that ten thousand swim freely in 

 that space ; consequently, a cubic inch of such an infusion 

 would contain more organised atoms than there are human 

 beings on the surface of the earth. When we reflect upon 

 the universal distribution of the Infusoria in the waters of 

 our planet, as well as in the juices of animals and plants, we 

 cease to be astonished at their omnipresence in nature, and 



FIG. 153 B. A portion of Fig. 152 

 magnified. 



A line is one twelfth of an inch. 



