1 84 GEOLOGICAL BIOLOGY. 



cies continuing so long as the race continued to reproduce in 

 its original integrity. With this theory there was no way to 

 account for species, except by assuming that the difference be- 

 tween two species is intrinsic, and is not to be accounted for 

 by the natural laws of reproduction. 



The problem of the origin of species came to be a ques- 

 tion for scientific investigation and speculation at the time 

 when the idea of fixity of those characters was replaced by 

 the theory that variability belonged to the specific as well as 

 to the so-called varietal characters. In other words, in dis- 

 cussing the origin of species we assume that reproduction is 

 not a process of exact, but of inexact repetition of characters, 

 or of imperfect reproduction of ancestral characters in the 

 offspring. 



Variability an Inherent Characteristic of all Organisms. — Vari- 

 ability is thus assumed to be an inherent characteristic of all 

 organisms, and origin of species has primarily to consider how 

 comparative permanency of characters, and of different sets of 

 characters in different lines of descent, is brought about. 



The Origin of Form, not of Matter.- — The origin of organic 

 matter takes us back to the earliest stage of the universe, and 

 as to a choice between a spontaneous origin from inorganic 

 matter, or an eternal existence of the two kinds of matter, 

 theories may differ, and for our purposes it is useless to in- 

 quire. Our search is for the origin of forms expressed by 

 organisms, and since our studies of paleontology present us 

 with an orderly procession of changing forms, it is quite le- 

 gitimate for us to seek among fossil forms for a scientific ex- 

 planation of the origin of the separate forms, which we call 

 species. 



Definition of Species whose Origin is Sought. — The definition 

 of species, quoted from Huxley, will suffice for the present 

 stage of this study of science: "The species regarded as 

 the sum of the morphological characters in question, and 

 nothing else, does not exist in nature ; but it is an abstrac- 

 tion, obtained by separating the structural characters in which 

 the actual existences, the individual crayfishes, agree, from 

 those in which they differ, and neglecting the latter." 



But again: " Species, in the strictly morphological sense, 



