increased deceptiveness so produced had frequently led to the overlooking
of its much persecuted possessor. But if we take the selection-value of
the initial stages for granted, we are confronted with the further question
which I myself formulated many years ago: How does it happen THAT THE
NECESSARY BEGINNINGS OF A USEFUL VARIATION ARE ALWAYS PRESENT? How could
insects which live upon or among green leaves become all green, while those
that live on bark become brown? How have the desert animals become yellow
and the Arctic animals white? Why were the necessary variations always
present? How could the green locust lay brown eggs, or the privet
caterpillar develop white and lilac-coloured lines on its green skin?

It is of no use answering to this that the question is wrongly formulated
(Plate, "Selektionsprinzip u. Probleme der Artbildung" (3rd edition),
Leipzig, 1908.) and that it is the converse that is true; that the process
of selection takes place in accordance with the variations that present
themselves. This proposition is undeniably true, but so also is another,
which apparently negatives it: the variation required has in the majority
of cases actually presented itself. Selection cannot solve this
contradiction; it does not call forth the useful variation, but simply
works upon it. The ultimate reason why one and the same insect should
occur in green and in brown, as often happens in caterpillars and locusts,
lies in the fact that variations towards brown presented themselves, and so
also did variations towards green: THE KERNEL OF THE RIDDLE LIES IN THE
VARYING, and for the present we can only say, that small variations in
different directions present themselves in every species. Otherwise so
many different kinds of variations could not have arisen. I have
endeavoured to explain this remarkable fact by means of the intimate
processes that must take place within the germ-plasm, and I shall return to
the problem when dealing with "germinal selection."