reciable changes have from time to time occurred, however they may have
been induced. Marked _races_ have undoubtedly so arisen (some striking
instances having been here recorded), and it is at least conceivable that
such may be the mode of _specific_ manifestation generally, the possible
conditions as to which will be considered in a later chapter. [Page 113]

* * * * *

CHAPTER V.

AS TO SPECIFIC STABILITY.

What is meant by the phrase "specific stability;" such stability to be
expected _a priori_, or else considerable changes at once.--Rapidly
increasing difficulty of intensifying race characters; alleged causes
of this phenomenon; probably an internal cause co-operates.--A certain
definiteness in variations.--Mr. Darwin admits the principle of
specific stability in certain cases of unequal variability.--The
goose.--The peacock.--The guinea fowl.--Exceptional causes of variation
under domestication.--Alleged tendency to
reversion.--Instances.--Sterility of hybrids.--Prepotency of pollen of
same species, but of different race.--Mortality in young gallinaceous
hybrids.--A bar to intermixture exists
somewhere.--Guinea-pigs.--Summary and conclusion.

As was observed in the preceding chapters, arguments may yet be advanced in
favour of the opinion that species are stable (at least in the intervals of
their comparatively sudden successive manifestations); that the organic
world consists, according to Mr. Galton's before-mentioned conception, of
many facetted spheroids, each of which can repose upon any one facet, but,
when too much disturbed, rolls over till it finds repose in stable
equilibrium upon another and distinct facet. Something, it is here
contended, may be urged, in favour of the existence of such facets--of such
intermitting conditions of stable equilibrium.

A view as to the stability of species, in the intervals of change, has been
well expressed in an able article, before quoted from, as follows:[104]--"A
given animal or plant appears to be contained, as it were, within a {114}
sphere of variation: one individual lies near one portion of the surface;
another individual, of the same species, near another part of the surface;
the average animal at the centre. Any individual may produce descendants
varying in any direction, but is more likely to produce descendants varying
towards the centre of the sphere, and the variations