28 THOUGHTS ON ANIMALCULES. 



VI. 



THE INFUSORIA, OR FRESH-WATER ANIMALCULES. 



From this sketch of the natural history of the Hydras, 

 we pass to the examination of the group of living animal- 

 cules sporting in the drops of water between the two 

 small plates of glass placed in the field of the microscope ; 

 and, as it comprises species of several families, it will 

 afford us a satisfactory elucidation of many interesting 

 particulars relating to the structure and economy of this 

 class of animals. To examine these objects in detail, we 

 must successively select a particular species, remove it 

 from the group, place it in a drop of pure water, and 

 inspect it under the microscope with different powers ; 

 beginning with a low magnifier, that we may first obtain 

 a general knowledge of the form and appearance of the 

 species, whether single or in clusters; and afterwards 

 examine the several parts of the body with the most 

 powerful glasses*. It was by patient and persevering 



* The scope of this volume does not admit of practical directions. Mr. 

 Andrew Pritchard's " Microscopic Illustrations" will be found to contain 

 the required information. 



