112 
DARWINISM. 
great difficulty connected with the Development Theory is its. 
application to those forms of life in which development seems to 
be of no service — at least for the course of several generations — 
until it is perfected, as, for instance, in the case of the electrical 
eel. Here, however, the law of correlation of structure may 
perhaps help us, for if, as I am inclined to believe, all variations 
are attended by a correlation of structure, then a variation in 
a given direction and possibly commencing from within, and 
attended by a corresponding correlation — both being advantageous 
to the fish — at length finds expression in what w^e call develop- 
ment in the formation of the electric organ. 
As to the future of Mr. Darwin’s theory, I am, I confess,, 
very hopeful, and cannot help believing that it will ultimately 
cover a much wider field than now, embracing man himself, 
with all his moral and intellectual faculties, as well as his mere 
physical form. Towards this, I think, all our scientific progress 
leads the way ; every newly-discovered fact in biology brings us 
nearer to the advent of a general recognition of the imminent 
presence throughout all life of a gradual evolution from lowest to 
highest, finding its expression in a thousand varied ways, yet 
manifesting through all the great key-note of unity in diversity. 
Why, of any two forms of life, both exposed to the same 
outward conditions, and both, perhaps, belonging to what we 
call the same species, should the one flourish and the other 
gradually become extinct? All that we can say is that wm 
do not know. But if we do not know the causes of extinction, 
if we cannot tell what those mysterious influences are, by 
reason of which a plant or animal becomes more and more rare, 
and finally disappears altogether, we surely have no right to be 
surprised at its extinction ; for, as Mr. Darwin has w'ell 
remarked, This is as if one should not be at all surprised 
at a man’s falling ill, or at his getting gradually worse, but 
should be amazed beyond measure at his ceasing to exist.” 
