On page 248, Vol. II., he says, "Throughout this chapter and elsewhere, I have spoken of selection as the paramount power; yet its action absolutely depends on what we in our ignorance call spontaneous or accidental variability."
Page 250: "Variation depends in a far higher degree on the nature or constitution of the being, than on the nature of the changed conditions."
On page 291, after giving cases of bud-variation, he says, "When we reflect on these facts, we become deeply impressed with the conviction that in such cases the nature of the variation depends but little on the conditions to which the plant has been exposed, and not in any especial manner on its individual character, but much more on the general nature or constitution, inherited from some remote progenitor of the whole group of allied beings to which the plant belongs. We are thus driven to conclude that in most cases the conditions of life play a subordinate part in causing any particular modification; like that which a spark plays when a mass of combustible matter bursts into flame—the nature of the flame depending on the combustible matter and not on the spark." And again, on page 288, "Now is it possible to conceive external conditions more closely alike than those to which the buds on the same tree are exposed? Yet one bud out of the many thousands borne by the same tree has suddenly, without any apparent cause, produced nectarines. But the case is even stronger than this; for the same flower-bud has yielded a fruit one half or a quarter a nectarine, and the other half or three quarters a peach. Again, seven or eight varieties of the peach have yielded, by bud variation, nectarines; the nectarines thus produced no doubt differed a little from each other; but still they are nectarines. Of course there must be some cause internal or external to excite the peach-bud to change its nature; but I cannot imagine a class of facts better adapted to force on our mind the conviction that what we call the external conditions of life are quite insignificant in relation to any particular variation, in comparison with the organization or constitution of the being which varies."
These assertions that there is something beyond the actions of the conditions of life are met with continually in his work, and they fully and conclusively show that he is no-wise inclined to adopt the mechanist theory. What alternative have we, then, but to conclude that this occult potent factor is reversion?
We have, we think, sufficiently shown that Darwin does not attribute variations solely to the conditions. But it has been asserted by the North American Reviewer, of whom we have often spoken, that Mr. Herbert Spencer declares them to be thus solely due. A dozen careful perusals of The Principles of Biology have failed to corroborate such a statement. On the contrary, Mr. Spencer on many occasions makes use of the phrase "spontaneous variations," though, apparently, under protest. It is true that throughout his work there is a constant insistance on the great part played by the physical conditions in causing variations. The greatest prominence is given to this factor. There is also a manifest desire that the mechanical forces be taken as adequate to the production of the phenomena. But nowhere is there clearly expressed a repudiation of the idea of concurrent cause. In some places there is a recognition of it.
Thus, on page 281, Mr. Darwin, after speaking of the action of the conditions of life, says, "Mr. Herbert Spencer has recently discussed with great ability this whole subject on broad and general grounds. He argues, for instance, that the internal and external tissues are differently acted on by the surrounding conditions, and they invariably differ in intimate structure; so, again, the upper and lower surfaces of true leaves are differently circumstanced with respect to light, etc., and apparently in consequence differ in structure. But, as Mr. Herbert Spencer admits, it is most difficult in all such cases to distinguish between the effects of the definite action of physical conditions and the accumulation through natural selection of inherited variations which are serviceable to the organism, and which have arisen independently of the definite action of these conditions."
It may be well to remark that the physical conditions are the sole cause of variation when viewed in their statical aspect; but when viewed in their dynamical aspect, the conditions are, except when the movement is in the direction of degeneration, only the secondary cause. For, upon the theory here enunciated, were all the individuals of a species fully developed, there would be but one race or variety, that is, the perfect type. The existence of a plurality of races or varieties necessarily implies the unfavorable modification of some of the parts or characters of some of the members of the species.
It is hardly possible for any one's common sense to be so impaired, even by speculation or the bias of a foregone conclusion, as to induce a belief that the characters given below have arisen solely by the action of the physical conditions. When the cases are isolated, such a belief is, in a small measure, excusable; but when they are given consecutively, the ascription of the characters solely to mechanical causes would imply not a little aberration of mind.
Numerous instances of bud-variation are given by Darwin. Several of these we have incidentally adverted to. By this process of bud-variation have arisen in one generation alone, and even in one season, nectarines from the peach, the red magnum bonum plum from the yellow magnum bonum, and the moss-rose from the Provence rose. Many other instances might be adduced of the appearance of characters equally strongly pronounced.
That the following characters have not arisen in one generation is confessedly owing to the lack of scientific knowledge as to the conditions requisite for their growth. The English lop-eared rabbit, which is under domestication, weighs not less than eighteen pounds. The pouter-pigeon is distinguished by the great size of its œsophagus; the English carrier-pigeon, by its surprisingly long beak; and the fantail, as its name connotes, by its immense upwardly-expanded tail. In the progenitor of these birds, the rock pigeon, (columba livia,) there is not a trace of these characters discernible. It is a matter of great surprise to look at the stringy roots of the wild carrot and parsnip, and then to note the astonishingly great improvement which has resulted from their subjection to more favorable conditions. Gooseberries have attained a great size and weight. The London gooseberry is now between seven and eight times the weight of the wild fruit. The fruit of one variety of the curcurbita pepo exceeds in volume that of another by more than two thousand fold!