TREVIRANUS. I93 



does not assign this as a cause of the origin of adap- 

 tations. Thus, many species become extinct, while 

 others become diminished in numbers. Man, him- 

 self, exhibits the direct modifying influence of his 

 environment by wide variations in his structure. 

 The history of the older geological periods is given 

 us in the succession of fossils. Here, Treviranus 

 added to the work of Cuvier the idea of modifica- 

 tion in time, an idea which Cuvier never adopted. 



Continuing to extend his Evolution theory (Vol. 

 III., p. 225), we find that he believed in Abioge- 

 nesis : — 



Every form of life can be produced by physical forces in one 

 of tivo ways : either by coming into being out of formless (inor- 

 ganic) matter, or by the modification of an already existing form 

 by a continued process of shaping. . . . Wherever Nature has 

 exerted her building forces she has brought forth Autochthones, 

 living bodies, 



. . . qui rupto robore nati, 

 Compositive Into, nullos habuere parentes. 



Wherever like conditions prevailed, of climate, earth, water, atmos- 

 phere, and a similar geographical position, these Autochthones 

 were similar, and the species which developed from them remained 

 similar as long as the environment was unaltered. But in studying 

 the form of any particular country, it is very hard to determine 

 which forms are native or autochthonous, and which have spread 

 into the country by migration from other countries. 



He then proceeds to anachronistic theories of the 

 abiogenetic origin of these Autochthones : — 



" But how did these species arise ? Were they born fully formed, 

 like Aphrodite, from sea-foam ? Or as simple zoophytes ? They 



