368 J- P- Lotsy. 



aus früher bereits vorhandenen anderen Arten hervorgegangen sind^ 

 wenn auch m. E. dieses Hervorgehen in anderer Weise geschah, wie- 

 er damals meinte. 



Zweiter Teil. 



Theoretisches. 



I. Der Ursprung der Arten nach Darwin. 



Darwin meint, daß zwischen Varietäten geringe, zwischen Arten> 

 größere Verschiedenheiten bestehen und sagt ^) : 



„The differences between natural varieties are slight whereas 

 the differences are considerable between the species of the same 

 genus and great between the species of distinct genera." 



Dann fragt er: 



„How do these lesser differences become augmented into 

 the greater difference? How do varieties or as I have called 

 them incipient species become converted into true and well- 

 defined species? 



Und sagt dann: 



„This problem of the conversion of varieties into species . . , 

 has been briefly treated in my „Origin of species". It was there 

 shown that all organic beings, without exception, tend to increase 

 at so high a ratio, that no district, no station, not even the 

 whole surface of the land or the whole ocean would hold the 

 progeny of a single pair after a certain number of generations. 

 The inevitable result is an ever-recurrent struggle for existence 

 Das führt zu einer Auswahl der am besten zugerüsteten Varie- 

 täten: „This preservation during the battle for life, of varieties 

 which possess any advantage in structure, constitution or instinct. 

 I have called Natural Selection . . . It'-) leads to the improve- 

 ment of each creature in relation to its organic and inorganic 

 conditions of life and consequently in most cases, to what must 

 be regarded as an advance in organisation." 

 Er weist dann daraufhin, daß die Naturwahl Divergenz verur- 

 sacht (ibid. p. 96): 



„Natural Selection also leads to Divergence of character; for 

 the more organic beings diverge in structure, habits and con- 



') Animals and Plants under domestication. Edition Murray, 8tli thousand, p. 5. 

 *) Origin of Species, p. 96. 



