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Show 132 LAWS OF VARIATION. CHAP. v. this system being functionally disturbed ~n the 1:~rents, I chiefly attribute the varying or plastiC condition of the offspring. The male and female sexual eleme~ts seem to be affected before that union takes place whwh is to form a new being. In the case of " sporting " plants the bud which in its earliest condition does not appar~ntly differ essentially from an ov~le, is alo~e affected. But why, because the reproductive system IS disturbed, this or that part should vary more or less, we are profoundly ignorant. Nevertheless, we can here and there dimly catch a faint ray of light, and we may feel sure that there must be some cause for each deviation of structure, however slight. Ho~ much direct effect difference of climate, food, &c., produces on any being is extremely doubtful. My impression is, that the effect is extremely small in the case of animals, but perhaps rather more in that of plants. We may, at least, safely conclude that such influences cannot have produced the many striking and complex co-adaptations of structure between one organic being and another, which we see everywhere throughout nature. Some little influence may be attributed to climate, food, &c. : thus, E. Forbes speaks confidently that shells at their southern limit, and when living in shallow water, are more brightly coloured than those of the same species further north or from greater depths. Gould believes that birds of the same species are more brightly eo loured under a clear atmosphere, than when living on islands or near the coast. So with insects, Wollaston is convinced that residence near the sea affects their colours. Moquin-Tandon gives a list of plants which when growing near the sea-shore have their leaves in some degree fleshy, though not elsewhere fleshy. Several other such cases could be given. The fact of varieties of one species, when they range CHAP. v. LAWS OF VARIATION. 133 into . t~e ~one of habitation of other species, often acquiring 1n a very slight degree some of the characters of s~ch· species, accords with our view that speeies of all kinds are only well-marked and permanent varieties. Thus the species of shells which are confined to tropical and shallow seas are generally brighter-coloured than those confined to cold and deeper seas. The birds which are. confined to continents are, according to Mr. Gould, bnghter-coloured than those of islands. The insect-species confined to sea-coasts, as every collector knows, are often brassy or lurid. Plants which live exclusively on the se~-side. are very apt to have fleshy l~aves .. He who beheves In the creation of each species, will have to say that this shell, for instance was created with bright colours for a warm sea· but that this other shell became bright-coloured b; variation when it ranged into warmer or shallower waters. When a variation is of the slightest use to a being, we cannot tell how much of it to attribute to the accumulative action of natural selection, and how much to the conditions of life. Thus, it is well known to furriers that animals of the same species have thicker and better fur the more severe the climate is under which they have lived; but who can tell how much of this difference may be due to the warmest-clad individuals having. been favoured and preserved during many generations, and how much to the direct action of the severe climate? for it would appear that climate has some direct action on the hair of our domestic quadrupeds. Instances could be given of the same variety being produced uuder conditions of life as different as can wel.l b.e conc.e ived ; and, on the other hand' of different vaneties being produced from the same species under the same conditions. Such facts show how indirectly |