96 
The Irish Naturalist, 
April, 
the different and, as it seems to me, conflicting conceptions 
which scientific men have put forward of the nature of the 
contest which every animal or plant has to sustain with its 
surroundings and with its own kind. 
We must all recognise that the life of every animal is beset 
with difficulties and dangers. That proposition is so obvious 
that it has been made the starting point of every believer in the 
theory of Natural Selection in his efforts to convey a clear idea 
of what that theory means. Darwin has told us — and has laid 
it down as a rule to which he says there can be no exception — 
that all animals are driven into competition with their ow^n 
kind in consequence of the rate at which they tend to increase. 
That proposition implies — and Darwin in more than one 
passage clearly accepts the inference --that there are as many 
animals in the world as the world can nourish. Every species 
of living creature, according to the Darwinian view, is at a 
high-water mark in point of numbers, in fact the world is 
congCvSted with it, so that whatever number of young it pro- 
duces during the course of the year, scarcity of food, or scarcity 
of something else that is competed for with equal keenness, 
will in the course of an average year have killed off all the 
overflow and reduced the total number back to what it was in 
the corresponding season last year. 
I do not know that any leading exponent of natural selection 
directly denies the truth of this conception of the struggle for 
existence ; but it is very customary to ignore it, and to argue 
upon an altogether different conception, according to which 
the natural tendency of animals is not to increase but to 
decrease. It is rather curious that the strongest upholder, so 
far as I know, of this anti-Darw4nian conception of the nature 
of the struggle is Professor Weismann, the great thinker and 
writer, who, in his enthusiastic advocacy of Darwin's main 
doctrine, \^ plus royaliste que leroi, the proclaimer of the "all- 
sufficiency of natural selection," while it seems to me that by 
the view he puts forward of the struggle for existence he cuts 
away much of the ground on which the most fdndamental 
articles of Darwin's teaching are based. 
For we must remember that if there is a limit of subsis- 
tence" for every species — as of course there must be — and if 
that limit has been reached — as Darwin supposes to be the 
