II 
ON THE TENDENCY OF VARIETIES, ETC. 
29 
to secure its safety, and to prolong its individual existence 
and that of the race. Such a variety could not return to the 
original form ; for that form is an inferior one, and could 
never compete with it for existence. Granted, therefore, a 
“tendency ” to reproduce the original type of the species, still 
the variety must ever remain preponderant in numbers, and 
under adverse physical conditions again alone survive. But 
this new, improved, and populous race might itself, in course 
of time, give rise to new varieties, exhibiting several diverging 
modifications of form, any of which, tending to increase the 
facilities for preserving existence, must, by the same general 
law, in their turn become predominant. Here, then, we have 
progression and continued divergence deduced from the general 
laws which regulate the existence of animals in a state of 
nature, and from the undisputed fact that varieties do fre- 
quently occur. It is not, however, contended that this result 
would be invariable ; a change of physical conditions in the 
district might at times materially modify it, rendering the 
race which had been the most capable of supporting existence 
under the former conditions now the least so, and even 
causing the extinction of the newer and, for a time, superior 
race, while the old or parent species and its first inferior 
varieties continued to flourish. Variations in unimportant 
parts might also occur, having no perceptible effect on the 
life-preserving powers ; and the varieties so furnished might 
run a course parallel with the parent species, either giving 
rise to further variations or returning to the former type. 
All we argue for is, that certain varieties have a tendency to 
maintain their existence longer than the original species, and 
this tendency must make itself felt ; for though the doctrine 
of chances or averages can never be trusted on a limited scale, 
yet, if applied to high numbers, the results come nearer to 
what theory demands, and, as we approach to an infinity 
of examples, become strictly accurate. Now the scale on 
which nature works is so vast — the numbers of individuals 
and the periods of time with which she deals approach 
so near to infinity — that any cause, however slight, and 
however liable to be veiled and counteracted by accidental 
circumstances, must in the end produce its full legitimate 
results. 
