ON THE HYPOTHESIS OF EVOLUTION. 129 



ations by more or less numerous points of structure, color, size, 

 etc., and by habits and instincts also, to a certain extent; that 

 the individuals of such associations reproduce their like, and can 

 not be produced by individuals of associations or species v^^hich 

 present differences of structure, color, etc., as defined by natural- 

 ists ; that the individuals of any such series or species are incapa- 

 ble of reproducing with those of any other species, with some 

 exceptions ; and that in the latter cases the offspring are usually 

 entirely infertile. 



The hypothesis of Cuvier assumes that each species was created 

 by divine power as we now find it at some definite point of geo- 

 logic time. The paleontologist holding this view sees, in accord- 

 ance therewith, a succession of creations and destructions marking 

 the history of life on our planet from its commencement. 



The development hypothesis states that all existing species 

 have been derived from species of pre-existent geological periods, 

 as offspring or by direct descent ; that there have been no total 

 destructions of life in past time, but only a transfer of it from 

 place to place, owing to changes of circumstance ; that the types 

 of structure become simpler and more similar to each other as we 

 trace them from later to earlier periods ; and that finally we reach 

 the simplest forms consistent with one or several original parent 

 types of the great divisions into which living beings naturally fall. 



It is evident, therefore, that the hypothesis does not include 

 change of species by hybridization, nor allow the descent of living 

 species from any other living species : both these propositions are 

 errors of misapprehension or misrepresentation. 



In order to understand the history of creation of a complex 

 being, it is necessary to analyze it and ascertain of what it con- 

 sists. In analyzing the construction of an animal or plant we 

 readily arrange its characters into those which it possesses in com- 

 mon with other animals or plants, and tliose in which it resem- 

 bles none other : the latter are its i7icUvidual characters, consti- 

 tuting its individuality. Next, we find a large body of characters, 

 generally of a very obvious kind, which it possesses in common 

 with a generally large number of individuals, which, taken col- 

 lectively, all men are accustomed to call a species ; these charac- 

 ters we consequently name specific. Thirdly, we find characters, 

 generally in parts of the body which are of importance in the ac- 

 tivities of the animal, or which lie in near relation to its mechan- 

 ical construction in details, which are shared by a still larger 



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