440) that a grass (Nostus Borbonicus) is so eminently variable in its floral organisation, that the varieties might serve to make a family with sufficiently numerous genera and tribes--a remark which shows that important organs must be here variable." _Species which vary little._ The preceding statements, as to the great amount of variation occurring in animals and plants, do not prove that all species vary to the same extent, or even vary at all, but, merely, that a considerable number of species in every class, order, and family do so vary.

It will have been observed that the examples of great variability have all been taken from common species, or species which have a wide range and are abundant in individuals.

Now Mr.Darwin concludes, from an elaborate examination of the floras and faunas of several distinct regions, that common, wide ranging species, as a rule, vary most, while those that are confined to special districts and are therefore comparatively limited in number of individuals vary least.

By a similar comparison it is shown that species of large genera vary more than species of small genera.

These facts explain, to some extent, why the opinion has been so prevalent that variation is very limited in amount and exceptional in character.