rat Wee DIVERGENT EVOLUTION THROUGH SEGREGATION. 
The Chinese Recorder (Shanghai), July, 1885, I use the following lan- 
guage: ‘* We see what natural selection can not explain by considering 
the nature of the process. The survival of the fittest results in the 
separate breeding of the fittest, and therefore in the increasing fitness 
of successive generations of survivors; but how can it account for the 
division of the survivors of one stock, occupying one country, into forms 
differing more and more widely from each other? To explain such a result 
we must find some other law. I am prepared to show that there is such a 
law arising out of the very nature of organic activities, a law of segrega- 
tion, bringing together those similarly endowed and separating them from 
those differently endowed.” 
Without variation there can be no segregate breeding; and with- 
out segregate breeding and heredity there can be no accumulation of 
divergent variations resulting in the formation of races and species. 
In producing divergent evolution the causes of variation and heredity 
are therefore as important as the causes of segregate breeding; and 
though I pass them by in my present discussion, I trust it will not be 
attributed to an under-estimate of their importance. Though I do not 
stop to discuss the causes of variation, my reasoning rests on the 
observed fact that in every deparment of the organic world variation 
is found, and that in the vast majority of cases, if not absolutely in all, 
the diversities to which any freely inter-generating group of organisms 
is subject follow the general law of ‘frequency of deviation from an 
average.” As this is a law according to which half of the members of 
the inter-generating group are above and half below the average in rela- 
tion to any character, there must often occur simultaneous variation of 
several individuals in some character which tends to produce segregate 
breeding. The reality and importance of this law is not at all depend- 
ent on the reality of any of the theories of heredity and variation that 
are now being discussed. Whatever may be the causes that produce 
variation, whether they depend entirely upon changes in external con- 
ditions or are chiefly due to changing activities in the organism and 
the hereditary effects of acquired characters, or are (as Weismann main- 
tains) the direct result of sexual reproduction which never transmits 
acquired characters—in any and every case this law of deviation from 
an average remains undisturbed and is recognized as an important fac- 
tor in the present paper. It therefore can not be urged that the theory 
here advanced assumes simultaneous variation without any ground for 
making such an assumption; nor can it be said that it rests on the 
incredible assumption that chance variation of very rare kinds will be 
duplicated at one time and place and will represent both sexes. 
Moritz Wagner first discussed what he calls ** The law of the migra- 
tion of organisms,” in a paper read before the Royal Academy of 
Sciences at Munich, in March, 1868; but my attention was not called 
to it till after the reading of my paper before the British Association 
in August, 1872. In a fuller paper entitled “‘The Darwinian Theory 
