192 
REV. J. T. GULICK ON DIVERGENT EVOLUTION 
conditions has power to winnow out whatever forms are least 
fitted to survive, there will usually remain a number of varieties 
equally fitted to survive ; and that through the law of segregation 
constantly operating in species distributed over considerable 
areas, these varieties continue to diverge both in form and in 
habits till separate species are fully established, though the con- 
ditions are the same throughout the whole area occupied by the 
diverging forms.” The conclusion reached was, that “ The theory 
that diversity of Natural Selection is, like variation, an essential 
factor in producing diversity of species, is untenable. On the 
contrary, we find that diversity of Natural Selection is not 
necessary to diversity of evolution, nor uniformity of Natural 
Selection to uniformity of evolution ; but while variation and 
separation are the essential factors in diversity , and intercrossing 
and unity of descent the essential agents in uniformity of evolu- 
tion, Natural Selection maybe an important ally on either side.” 
In an article on “ Evolution in the Organic World,” published 
in ‘ The Chinese Recorder ’ (Shanghai), July 1885, I use the fol- 
lowing language: — “We see what Natural Selection cannot 
explain by considering the nature of the process. The sur- 
vival 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 survi~ 
vors 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 laic rising out of the very nature of organic activities , a law of 
Segregation , bringing together those similarly endowed , and sepa- 
rating them from those differently endowed .” 
Without Variation there can be no Segregate Breeding; and 
without Segregate Breeding and Heredity there can be no accu- 
mulation 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 department 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 intergenerating group of 
