THE FUxVC TIONS OF LIFE. 4 



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position of one part of a system of bodies occasions 

 a change in the centres of gravity, of gyration, and 

 of oscillation ; and evolves new mechanical forces 

 and conditions of equilibrium, which render new 

 adjustments in other parts necessary, in order to 

 restore the equipoise, and preserve the harmony 

 of their movements. 



We may conclude from these inquiries that the 

 numerous classes or assemblages of beings, which 

 science has formed, are by no means arbitrary 

 creations of the human mind, invented merely with 

 a view to facilitate the study and to recognise the 

 identity of species, or calculated only to supply the 

 imperfections of our memory ; but that they have a 

 real foundation in nature. To regard any of the 

 beings in the creation as isolated from the rest, 

 would be to take a very narrow and a false view of 

 their condition ; for all are connected by mutual 

 relations. Even among the leading types which 

 represent the great divisions of the animal kingdom 

 we may trace several points of resemblance, which 

 show them to be parts of one general plan, and to 

 have emanated from the same Creator. In the 

 progress of discovery we are continually meeting 

 with species which occupy intermediate places be- 

 tween adjacent types, and appear as links of con- 

 nexion in the chain of being. It often happens, 

 as I shall hereafter have occasion to point out, that 

 throughout an extensive series of organic forms, 

 the steps of gradation by which one type passes 

 into another, are so numerous and so regular, as 

 to preclude the possibility of drawing a decided line 

 of demarcation between those that properly apper- 

 tain to each. 



