HOLOGY:
EMBRYOLOGY: RUDIMENTARY ORGANS.

CLASSIFICATION, groups subordinate to groups. Natural system. Rules and
difficulties in classification, explained on the theory of descent
with modification. Classification of varieties. Descent always used in
classification. Analogical or adaptive characters. Affinities, general,
complex and radiating. Extinction separates and defines groups.
MORPHOLOGY, between members of the same class, between parts of the same
individual. EMBRYOLOGY, laws of, explained by variations not supervening
at an early age, and being inherited at a corresponding age. RUDIMENTARY
ORGANS; their origin explained. Summary.

From the first dawn of life, all organic beings are found to resemble
each other in descending degrees, so that they can be classed in groups
under groups. This classification is evidently not arbitrary like the
grouping of the stars in constellations. The existence of groups would
have been of simple signification, if one group had been exclusively
fitted to inhabit the land, and another the water; one to feed on flesh,
another on vegetable matter, and so on; but the case is widely different
in nature; for it is notorious how commonly members of even the same
subgroup have different habits. In our second and fourth chapters, on
Variation and on Natural Selection, I have attempted to show that it is
the widely ranging, the much diffused and common, that is the dominant
species belonging to the larger genera, which vary most. The varieties,
or incipient species, thus produced ultimately become converted, as I
believe, into new and distinct species; and these, on the principle
of inheritance, tend to produce other new and dominant species.
Consequently the groups which are now large, and which generally include
many dominant species, tend to go on increasing indefinitely in size.
I further attempted to show that from the varying descendants of each
species trying to occupy as many and as different places as possible in
the economy of nature, there is a constant tendency in their characters
to diverge. This conclusion was supported by looking at the great
diversity of the forms of life which, in any small area, come into the
closest competition, and by looking to certain facts in naturalisation.

I attempted also to show that there is a constant tendency in the forms
which are increasing in number and diverging in character, to supplant
and exterminate the less divergent, the less impr