220 



THE ANIMAL KINGDOM. 



power of generating from these materials the organic 



compounds which they require for 



their own development, and these 



are such as are formed by other 



undoubted protophytes, as is proved 



by the application of the appropriate 



tests." These " Desmidiacese " were 



long considered to belong to the 



animalculse, as were the " Diato- 



maceae," "Volvox globator" (fig. 



2), Ac. 



Some of the Infusoria, however, have 

 a far higher organisation, such as the " Botiferse," and espe- 

 cially the " wheel animalcule " (fig. 3), which at one time was 

 supposed, absurdly enough, to possess a living wheel turning 

 round rapidly on its head! This wheel, however, proved to be 

 nothing else than a vortex of water produced by rotatory cilia. 



FIG. 2. VOLVOX GLOBATOE. 



PIG. 3. -WHEEL ANIMALCULE ("Rotifer vulgaris). 



This and many other mistakes were owing to the imperfect 

 construction of the microscopes of that date. These 

 and their fellow animalcules possess several organs, as a 

 stomach, &c. The protozoa at one time were supposed to 

 possess a number of stomachs, and were thence called " poly- 

 gastric infusoria," but it has now been demonstrated that 

 these beings merely absorb or entangle portions of organic 

 matter into their substance, and that there are no cysts or 

 stomachs for their reception. Some of the Infusoria are able 

 to withtstand enormous changes of temperature, without 

 losing their vitality ; cold far below freezing point, and heat 

 equal to boiling water does not destroy them, and they may 

 be dried in the most complete manner which chemists can 

 devise, and kept in this dry state for years, and yet, on the 



