42 
The result being “ Natural selection, entailing divergence of 
character and the extinction of less improved forms” * Is it 
possible for these elements, in their mutual action and re- 
action, to occasion specific differences in living beiugs . Ihis 
is our first inquiry ; for the solution of which it is manifestly 
necessary that we should understand clearly what is meant by 
specific differences — what is meant by a species. We may 
define it roughly by saying that a species is a race ol living 
beings differing in certain respects from all other races, such 
differences being steadily transmissible by reproduction, and 
not being the immediate result of present outward conditions. 
By this definition are excluded— (1) all mere transient sports, 
and (2) all apparent varieties dependent directly upon situa- 
tion, climate, &c. To many it will doubtless seem far too lax 
a definition, as raising a large number of so-called varieties 
into the rank of species. Let such afford a better one, 
equally sufficient and equally free from arbitrary assertion. 
The great thing we have to beware of is allowing prejudice 
to lay down a definition which shall beg the question at issue, 
e . g., that specific differences are those which are permanently 
invariable ; that species are those races which are not bound 
together with intermediate varieties, or which cannot be 
traced to a common origin, or which, when crossed, y iela 
sterile hybrids. To discuss the natural origin of species with 
such definitions as the basis would be as impossible and 
absurd as to discuss the motions of the fixed stars with the 
definition given that the fixed stars are those which never 
move. The only fair definition of a species is a race of living 
beings possessing common characteristic differences from all 
others, which differences at the present time are constant and 
inherent. . 
That species grow and reproduce, that they pass on their 
characteristics by inheritance, and that they are liable to 
variation, is admitted by every one. The point at issue is 
whether they can so pass on and accumulate their variations 
by inheritance as in the end to bring about specific differences. 
'If they can do so, then the Darwinian hypothesis of the 
origin of species is, so far, possible ; variation and inheritance 
could bring about specific differences. 
Our attention must in the first place be directed to the, 
formation of breeds among domesticated animals and culti- 
vated plants. It is notorious that there have been produced 
by the agency of man distinct races of living beings, having 
characteristic differences from all others, which differences 
“ Origin of Species,” 4th edit., p. 577. 
