THE ARCTIC ANIMALCULE. 285 



mals themselves not exserted like the polypes (Hydra), 

 which is the case in the Alcyonium.* 



CLASS.— ANIMALCULE, 



OR THE 



ANIMALCULE OF THE POLAR REGIONS. 



These constitute a class of very diminutive animals, which 

 in general are invisible without the aid of a microscope. 

 They are, however, usually divided into three distinct sec- 

 tions, viz. the visible, microscopical, and invisible: the first, 

 though visible, cannot be accurately discerned without the 

 help of glasses ; the second are only discoverable by the 

 microscope ; and the last are merely presumed to exist, as 

 they are still unknown. The existence of the latter cannot 

 well be disputed, though it cannot be asserted, unless we 

 conclude that the microscope has arrived to the highest de- 

 gree of perfection. Reason and analogy give some support 

 to the conjectures of naturalists in this respect; animalcules 

 are discerned of various sizes, from those which are visible 

 to the naked eye to such as appear only like moving points 

 under the most powerful miscroscopic lenses ; therefore, it 

 is not unreasonable to imagine, therefore, that there are 

 many others that still resist the action of the microscope, as 

 the fixed do that of the telescope with the greatest powers 

 hitherto invented. 



Among" the visible animalculae are included an amazing 

 variety of creatures by no means of an analogous nature. 

 Those numerous animals which crowd the water in the sum- 

 mer months, changing it sometimes to a deep or pale red 



* Captain Phipp's Voyage, p. 199. 



