Ortmann.] -1-^^ [May 15, 



But if we analyze the action of man iu breeding, we shall find that it does 

 not correspond to natural selection, but is more complex, and that 

 accordingly the final result obtained by man is different from that in 

 nature. 



The breeder selects from a certain species a number of individuals 

 fitted for his particular intentions. The whole number of individuals of 

 this species is thus divided into two parts : the selected and the rejected. 

 By natural selection also the individuals of a species are divided into two 

 parts: Ww fitted ?ind ihe unfitted. There seems to be complete analogy, 

 but this is not the case. In natural selection, as we have seen above, 

 the fitted survive, and the unfitted are destroyed. But iu man's selection 

 there is a difference: of course, the selected corresponding to the fitted 

 survive, but the rejected corrresponding to the unfitted are not invariably 

 destroyed. On the contrary, they survive too, at least a great number of 

 them. It is not at all in the breeder's power to kill all the individuals 

 not wanted of the species under domestication ; he may kill of a particu- 

 lar litter, perhaps of all his stock those not corresponding to his wishes, 

 he may continue this killing during a series of generations, but he never 

 can succeed in destroying all the rejected individuals of the original spe- 

 cies with which he deals. On the contrary, this original species will pro- 

 pagate, and will continue to exist beside the new race obtained from it. 

 The result of the breeder's art is a new race coexisting with the original 

 species. 



See the difference. Natural selection preserves only a number of indi- 

 viduals possessing a certain number of useful characters, while all the 

 others are destroyed: it preserves the good standard of the species or may 

 even improve it. Man's selection, however, gives origin to a new race 

 branching off" from the original species, which is preserved, too, and may 

 be subject for itself to the action of natural selection or may be domesti- 

 cated and subject to breeding again. Therefore, it is easily understood, 

 that it is certainly incorrect to look upon natural selection and the art 

 of the breeder as analogous processes, and natural selection cannot be the 

 cause of the origin of different species. 



We may, however, safely say that the races obtained by the breeder 

 are analogous to natural species, and we are to examine by what addi- 

 tional lactors the complete parallelism of the breeding of races and the 

 formation of different species in nature is accomplished. 



Recently* I have endeavored to demonstrate that we are to imagine 

 natural selection supplemented by the process of Separation (or Isola- 

 tion), in order to understand the development of coexisting different spe- 

 cies from one original species. The main point in separation is the action 

 of different conditions of life in different localities separated from each 

 other. The descendants of one ancestral form, if separated under different 

 conditions, tend to develop separately, and the directions of either muta- 

 tion or orthogenesis become different in each separated group : another 



* Qrandzugc der marinen Ticrgeographie, pp. 31, 32. 



