End of the observation

Usage examples of differences.

I think, at least safely infer that diversification of structure, amounting to new generic differences, would have been profitable to them.

A large amount of inheritable and diversified variability is favourable, but I believe mere individual differences suffice for the work.

But in regard to the differences both in the internal and external structure of the seeds, which are not always correlated with any differences in the flowers, it seems impossible that they can be in any way advantageous to the plant: yet in the Umbelliferae these differences are of such apparent importance--the seeds being in some cases, according to Tausch, orthospermous in the exterior flowers and coelospermous in the central flowers,--that the elder De Candolle founded his main divisions of the order on analogous differences.

Possibly, these several differences may be connected with some difference in the flow of nutriment towards the central and external flowers: we know, at least, that in irregular flowers, those nearest to the axis are oftenest subject to peloria, and become regular.

These alone are the unimportant differences, which Gartner is able to point out, between hybrid and mongrel plants.

Chapter VIII Hybridism Distinction between the sterility of first crosses and of hybrids -- Sterility various in degree, not universal, affected by close interbreeding, removed by domestication -- Laws governing the sterility of hybrids -- Sterility not a special endowment, but incidental on other differences -- Causes of the sterility of first crosses and of hybrids -- Parallelism between the effects of changed conditions of life and crossing -- Fertility of varieties when crossed and of their mongrel offspring not universal -- Hybrids and mongrels compared independently of their fertility -- Summary.

The foregoing rules and facts, on the other hand, appear to me clearly to indicate that the sterility both of first crosses and of hybrids is simply incidental or dependent on unknown differences, chiefly in the reproductive systems, of the species which are crossed.

Compare the English carrier and the short-faced tumbler, and see the wonderful difference in their beaks, entailing corresponding differences in their skulls.

Many slight differences might, and indeed do now, arise amongst pigeons, which are rejected as faults or deviations from the standard of perfection of each breed.

Some authors believe it to be as much the function of the reproductive system to produce individual differences, or very slight deviations of structure, as to make the child like its parents.

Chapter II Variation under Nature Variability -- Individual Differences -- Doubtful species -- Wide ranging, much diffused, and common species vary most -- Species of the larger genera in any country vary more than the species of the smaller genera -- Many of the species of the larger genera resemble varieties in being very closely, but unequally, related to each other, and in having restricted ranges.

Chapter XI Geographical Distribution Present distribution cannot be accounted for by differences in physical conditions -- Importance of barriers -- Affinity of the productions of the same continent -- Centres of creation -- Means of dispersal, by changes of climate and of the level of the land, and by occasional means -- Dispersal during the Glacial period co-extensive with the world.

Moreover, on the view of the origin of genera which I shall presently give, we have no right to expect often to meet with generic differences in our domesticated productions.

We can, I think, further understand the frequently abnormal character of our domestic races, and likewise their differences being so great in external characters and relatively so slight in internal parts or organs.

Nor must the value which would formerly be set on any slight differences in the individuals of the same species, be judged of by the value which would now be set on them, after several breeds have once fairly been established.