288 Darwin, and after Darwin. 
upon no other theory can its universality and invari- 
ability be rendered intelligible. On the beneficent 
design theory, for instance, it is inexplicable that no 
species should ever be found to present a structure or 
an instinct having primary reference to the welfare of 
another species, when, ex hypothesz, such an endless 
amount of thought has been displayed in the creation 
of structures and instincts having primary reference to 
the species which present them. For how magnificent 
a display of divine beneficence would organic nature 
have afforded, if all—or even some—species had been 
so inter-related as to have ministered to each others 
wants. Organic species might then have been likened 
to a countless multitude of voices, all singing in one 
great harmonious psalm. But, as it is, we see abso- 
lutely no vestige of such co-ordination: every species 
is for itself, and for itself alone—an outcome of the 
always and everywhere fiercely raging struggle for 
life. 
In order that the force of this argument may not be 
misapprehended, it is necessary to bear in mind that 
it is in no way affected by cases where a structure or 
an instinct is of primary benefit’ to its possessor, and 
then becomes of secondary benefit to some other species 
on account of the latter being able in some way or 
another to utilise its action. Of course organic nature 
is full of cases of this kind ; but they only go to show 
the readiness which all species display to utilise for 
themselves everything that can be turned to good ac- 
count in their own environments, and so, among other 
things, the structures and instincts of other animals. For 
instance, it would be no answer to Darwin’s challenge if 
any one were to point to a hermit-crab inhabiting the 
