90 STUDIES IN AJSriMAL LIFE. 



In the attempts to construct a system, naturalists 

 are commonly said to have followed two metliods, 

 the artificial and the natural. The artificial method 

 seizes some one prominent characteristic, and groups 

 aU the individuals together which agree in this one 

 respect. In Botany the artificial method classes 

 plants according to the organs of reproduction ; but 

 this has been found so very imperfect that it has 

 been abandoned, and the natural method has been 

 substituted, according to which the whole structure 

 of the plant determines its place. If flying were 

 taken as the artificial basis for the grouping of some 

 animals, we should find insects and birds, bats and 

 flying squirrels grouped together; but the natural 

 method, taking into consideration not one character, 

 but all the essential characters, finds that insects, 

 birds, and bats differ profoundly in their organiza- 

 tion : the insect has wings, but its wings are not 

 formed like those of the bird, nor are those of the 

 bird formed like those of the bat. The insect does 

 not breathe by lungs, like the bird and the bat ; it 

 has no internal skeleton, like the bird and the bat ; 

 and the bird, although it has many points in com- 

 mon with the bat, does not, like it, suckle its young; 

 and thus we may run over the characters of each 

 organization, and find that the three animals belong 

 to widely different groups. 



It is to Linnaeus that we are indebted for the 

 most ingenious and comprehensive of the many 

 schemes invented for the cataloguing of animal 



