112 REPORT—1862. 
atmospheric ocean which are now buried in the form of coal and other fossil remains, 
as well as that far greater mass of animal and vegetable excrement and of other 
organic matter sine ts mingled with the inorganic substance of the earth’s crust, 
and is composed in a great measure of ingredients abstracted from the atmosphere. 
Look again at the changes produced in the conditions of the existence of each 
animal by all organized beings inhabiting the same area. Some devour it, others are 
devoured by it; some become more scarce, others more plentiful; some exercise a 
beneficial, others an injurious influence on it; but all are in some =, changing its 
conditions of existence, and all are being in their turn changed, as Mr. Darwin has 
so ably pointed out, by the struggle for existence and the process of natural 
selection. Again, all of them extract from the soil, directly or directly, some of 
its nutritious constituents, and return them to it in different forms, in different 
places, and under different chemical combinations. Add to all these other causes 
of change the action of the being itself in altering its own conditions of existence, 
and it will at once be evident that, in the course of such long periods of time as we 
have referred to, striking and marked changes must be produced in the conditions 
of existence of almost every species. 
Hence it follows that if we suppose a group of beings to be at one period of their 
history in harmony with the conditions of their existence, they must at all subse- 
quent periods be more and more out of harmony with it; and that, on the suppo- 
sition of the invariability of the species, this discrepancy between the species and 
its environment must at length become so great that its extinction must become 
inevitable. It necessarily follows from this, that there must be on the part of the 
species a constant instinctive, though perhaps unconscious, effort to restore the lost 
equilibrium, to get rid of the sufferings which will arise from the want of it, and 
to place itself once more in harmony with its conditions of existence; and the 
greater the change in the conditions, the more strenuous will this effort be. Some 
one once remarked to Coleridge, “ All things find their level.” “No,” replied that 
great man, “all things are finding their level like water in a storm.” This saying 
appears to me to describe, with the happiness of genius, the nature of the incessant 
movement that is always going on in all parts of the world, and amongst almost all 
its animal and vegetable inhabitants. All are unconsciously striving to keep them- 
selves in harmony with a medium which is continually changing. 
In order, then, that they may not be utterly distanced by the ever-changing con- 
ditions of their existence so as in time to become extinct, they must possess a 
capacity for variation in the direction of those changes which is absolutely illimit- 
abla: provided only that sufficient time be allowed for its development. That they 
do possess such a capacity to a certain extent has been triumphantly demonstrated 
by eres The real question is, Are there any, and, if so, what, limits to this 
capacity of variation in the direction of actual or possible changes in the conditions 
of existence ? Now, in reference to this question, it seems to me that Mr. Darwin 
has not sufficiently distinguished between a capacity for variation and a tendency 
to vary, which, I would submit, are two very different things. I would respectfully 
contend that the capacity for variation is in the being; but the tendency to 
vary arises out of the changes which take place in the conditions of existence, and 
in the efforts unconsciously made by the being to overtake those changes. When, 
therefore, a species of animals inhabit the same area, they will, generally speaking, 
be exposed to nearly the same changes in the conditions of their existence. This 
will almost necessarily lead-to similar variations manifesting themselves in the 
same individuals at the same time, because they will all be exposed to the same 
changes, and variations thus produced are much more likely to be strengthened and 
perpetuated than varieties arising from temporary causes, or such as affect indivi- 
duals only. Mr. Darwin says, ‘“ When a variation is of the slightest use to a being, 
we cannot tell how much of it to attribute to the accumulative action of natural 
selection, and how much to the conditions of life ;” and a little further on, “ Such 
considerations as these incline me to lay very little weight on the direct action of 
the conditions of life. Indirectly, as already remarked, they seem to play an im- 
portant part in affecting the reproductive system ; and in thus inducing variability 
and natural selection, will then accumulate all profitable variations, however slight, 
until they become plainly developed and appreciable by us.” 
