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Show 398 PROVISIONAL HYPOTHESIS CH.AP. XXVII. in any way improbable, for, though a vast number of active and long-dormant gemmules are diffused and nourished in each living creature, yet there must be some limit to their number; and it appears natural that gemmules derived from an enfeebled and useless rudiment would be more liable to perish than those derived from other parts which are still in full functional activity. With respect to mutilations, it is certain that a part may be removed or injured during many generations, and no inherited result follow; and this is an apparent objection to the hypothesis which will occur to every one. But, in the first place, a being can hardly be intentionally mutilated during its early stages of growth whilst ·in the womb or egg; and such mutilations, when naturally caused, would appear like congenital deficiencies, which are occasionally inherited. In the second place, according to our hypothesis, gemmules multiply by self-division and are transmitted from generation to generation; so that during a long period they would be present and ready to reproduce a part which was repeatedly amputated. Nevertheless it appears, from the facts given in the twelfth chapter, that in some rare cases mutilations have been inherited, but in most of these the mutilated surface became diseased. In this case it may be conjectured that the gemmules of the lost part were gradually all attracted by the partially diseased surface, and thus perished. Although this would occur in the injured individual alone, and therefore in only one parent, yet this might suffice for the inheritance of a mutilation, on the same principle that a hornless animal of either sex, when crossed with a perfect animal of the opposite sex, often transmits its deficiency. The last subject that need here be discussed, namely Reversion, rests on the principle that transmission and development, though generally acting in conjunction, are distinc.t powers; and the transmission of gemmules and their subsequent development show us how the existence of these two distinct powers is possible. We plainly see this distinction in the many cases in which a grandfather transmits to his grandson, through his daughter, characters which she does not, or cannot, possess. Why the development of certain characters, not necessarily in any. way connected with the reproductive organs, should be confined to one sex alone-that is, why certain cells in one sex CHAP. XXVII. OF PANGENESIS. 399 should unite with and cause the development of certain gemmules- we do not in the least know; but it is the common attribute of most organic beings in which the sexes are separate. The distinction between transmission and development is bkewise seen in all ordinary cases of Reversion; but before discussing this subject it may be advisable to say a few words on those characters which I have called latent, and which would not be classed under Reversion in its usual sense. Most, or perhaps all, the secondary characters, which appertain to one sex, lie dormant in the other sex; that is, gemmules capable of development into the secondary male sexual characters are included within the female ; and conversely female cha-" racters in the male. Why in the female, when her ovaria become diseased or fail to act, certain masculine gemmules become developed, we do not clearly know, any more than why when a young bull is castrated his horns continue growing until they almost resemble those of a cow; or why, when a stag is castrated, the gemmules derived from the antlers of his progenitors quite fail to be developed. But in many cases, with variable organic beings, the mutual affinities of the cells and gemmules become modified, so that parts are transposed or multiplied; and it would appear that a slight change in the constitution of an animal, in connection with the state of the reproductive organs, leads to changed affinities in the tissues of various parts of the body. Thus, when male animals first arrive at puberty, and subsequently during each recurrent season, certain cells or parts acquire an affinity for certain gemmules, which become developed into the secondary masculine characters; but if the reproductive organs be destroyed, or even temporarily disturbed by changed conditions, these affinities are not excited. Nevertheless, the male, before he arrives at puberty, and during the season when the species does not breed, must include the proper gemmules in a latent state. The curious case formerly given of a Hen which assumed the masculine characters, not of her own breed but of a remote progenitor, illustrates the connexion between latent sexual characters and ordinary reversion. With those animals and plants which habitually produce several forms, as with certain butterflies described by Mr. Wallace, in which three female forms and |
