able equilibrium. This is the conception of Mr.
Galton,[76] who compares the development of species with a many {98}
facetted spheroid tumbling over from one facet, or stable equilibrium, to
another. The existence of internal conditions in animals corresponding with
such facets is denied by pure Darwinians, but it is contended in this work,
though not in this chapter, that something may also be said for their
existence.

The considerations brought forward in the last two chapters, namely, the
difficulties with regard to incipient and closely similar structures
respectively, together with palaeontological considerations to be noticed
later, appear to point strongly in the direction of sudden and considerable
changes. This is notably the case as regards the young oysters already
mentioned, which were taken from the shores of England and placed in the
Mediterranean, and at once altered their mode of growth and formed
prominent diverging rays, _like those of the proper Mediterranean oyster_;
as also the twenty-nine kinds of American trees, all differing from their
nearest European allies _similarly_--"leaves less toothed, buds and seeds
smaller, fewer branchlets," &c. To these may be added other facts given by
Mr. Darwin. Thus he says, "that climate, to a certain extent, directly
modifies the form of dogs."[77]

The Rev. R. Everett found that setters at Delhi, though most carefully
paired, yet had young with "nostrils more contracted, noses more pointed,
size inferior, and limbs more slender." Again, cats at Mombas, on the coast
of Africa, have short stiff hairs instead of fur, and a cat at Algoa Bay,
when left only eight weeks at Mombas, "underwent a complete metamorphosis,
having parted with its sandy-coloured fur."[78] The conditions of life seem
to produce a considerable effect on horses, and instances are given by Mr.
Darwin of pony breeds[79] having independently arisen in different parts of
the world, possessing a certain similarity in their physical {99}
conditions. Also changes due to climate may be brought about at once in a
second generation, though no appreciable modification is shown by the
first. Thus "Sir Charles Lyell mentions that some Englishmen, engaged in
conducting the operations of the Real del Monte Company in Mexico, carried
out with them some greyhounds of the best breed to hunt the hares which
abound in that country. It was found that the greyhounds could not support
the fatigues o