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 Avhich, 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. 



