THEOUGH CUMULATIVE SEGItEGATION. 



219 



As a convenient method of illustration, let us consider the 

 different results that will be gained according as we subject the 

 same ten pairs of wild rock-pigeons to one or the other of the 

 following methods of treatment. 



In the first experiment let the treatment be as follows : — Let 

 ten aviaries be prepared ; and in each aviary put one male with 

 the female that most nearly resembles it. When the young of 

 each aviary arrive at maturity, let them be inspected, and if any 

 individual resembles the inmates of one of the other aviaries 

 more than the inmates of the aviary in wliieh it was produced, 

 let it be placed with those it most closely resembles. If any 

 unusual variation arises, let it be placed in a new aviary, and let 

 the one of the other sex that most closely resembles it in that 

 respect be placed with it. When the crowding in any aviary 

 becomes injurious to the health of the birds let the numbers be 

 indiscriminately reduced. Let this process be continued many 

 generations, the inmates in all the aviaries being fed on the same 

 food, and in every respect treated alike, and what will be the 

 result ? 



No experienced breeder will hesitate in assuring us that under 

 such treatment a multitude of varieties will be formed, many of 

 which will be very widely divergent from the original wild stock. 

 In other words, Cumulative Segregation will produce accumulated 

 divergence, though there is no Selection in the sense in ivhich 

 Natural Selection is Selection. 



Again, let us take the same ten pairs, and putting them into 

 one large aviary, let them breed freel} together without any 

 Segregative influence coming in to affect the result ; and who 

 does not know that the type would remain essentially one 

 though a considerable range of individual variation might arise. 

 That is, without Segregation no divergence of type ivill arise. 



The Natueal Law of Cumulative Segeegation. 



I shall now show that there is in nature a law of Cumulative 

 Segregation. There are large classes of activities in the organism 

 and in the environment that conspire to produce Segregate 

 Breeding ; and to produce it in such a w ay that, in a vast mul- 

 titude of cases, it becomes a permanent fact, which no cause 

 that we are acquainted with can ever obliterate. Moreover, 

 when one form of Segregation has become fully established, we 



