s colors of the eggs of birds and of the hair and
feathers of animals which are adapted to the purpose of concealment.
"Thus the snake, and wild cat, and leopard are so colored as to resemble
dark leaves and their light interstices" (p. 248). The eggs of
hedge-birds are greenish, with dark spots; those of crows and magpies,
which are seen from beneath through wicker nests, are white, with dark
spots; and those of larks and partridges are russet or brown, like their
nests or situations. He adds: "The final cause of their colors is easily
understood, as they serve some purpose of the animal, but the efficient
cause would seem almost beyond conjecture." Of all this subject of
protective mimicry thus sketched out by the older Darwin, we find no
hint or trace in any of Lamarck's writings.

8. Great length of time. He speaks of the "great length of time since
the earth began to exist, perhaps millions of ages before the
commencement of the history of mankind" (p. 240).

In this connection it may be observed that Dr. Darwin emphatically
opposes the preformation views of Haller and Bonnet in these words:

"Many ingenious philosophers have found so great difficulty in
conceiving the manner of the reproduction of animals that they have
supposed all the numerous progeny to have existed in miniature in
the animal originally created, and that these infinitely minute
forms are only evolved or distended as the embryon increases in the
womb. This idea, besides being unsupported by any analogy we are
acquainted with, ascribes a greater tenuity to organized matter than
we can readily admit" (p. 317); and in another place he claims that
"we cannot but be convinced that the fetus or embryon is formed by
apposition of new parts, and not by the distention of a primordial
nest of germs included one within another like the cups of a
conjurer" (p. 235).

9. To explain instinct he suggests that the young simply imitate the
acts or example of their parents. He says that wild birds choose spring
as their building time "from the acquired knowledge that the mild
temperature of the air is more convenient for hatching their eggs;" and
further on, referring to the fact that seed-eating animals generally
produce their young in spring, he suggests that it is "part of the
traditional knowledge which they learn from the example of their
parents."[156]

10. Hybridity. He refers in a cursory way to the changes produced by the
mi