164 CLASSIFICATION. 



within these, vacuoles may often be seen to form 

 spontaneously. 



The Infusoria may be collected in small phials ; but 

 it is difficult to keep them, as they form the food of 

 the Entomostraca, the Rotatoria, and the larvae of 

 insects ; so that their enemies are very numerous, and 

 they soon disappear. 



CLASSIFICATION. Before leaving the subject of 

 living bodies, it may be well to make a few remarks 

 upon their systematic relation as denned by classi- 

 fication. 



All natural bodies are referable to one of three 

 great kingdoms, viz. the Animal, the Vegetable, or 

 the Mineral Kingdom. The bodies belonging to the 

 latter seldom come under the notice of the micro- 

 scopic observer, as they are mostly visible to the 

 naked eye, and their minute structure is the same as 

 that of the larger masses. The general structure of 

 the members of the vegetable and animal kingdoms 

 has been illustrated in the preceding pages. These 

 bodies are distinguished from those of the mineral 

 kingdom by their vital power of appropriating sur- 

 rounding matters to their own nutrition and growth 

 this power being exercised by their organs, or, in the 

 lowest forms, by any portion of their substance. 

 Hence animals and vegetables or plants are termed 

 organic bodies, while minerals are termed inorganic 

 bodies, as having no organs; and the material of 

 which organic bodies consist is termed organic mat- 

 ter, that of minerals being inorganic matter. But in 

 both animals and plants inorganic matter is mixed 

 with the organic matter, having been taken up or 

 absorbed from the inorganic kingdom, although it 

 does not usually exist in its characteristic condition, 

 which is that of crystals, i. e. angular solids, as crystals 

 of Epsom salts, &c. The individual members of the 



