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Show 124 TilE DESCENT OF 1\f.AN. l'.un I. grow into two distinct uteri, each with a well-constructed orifice and passage, and each furnished with numerous muscles, nerves, glands and vessels, if they had not formerly passed through a similar course of development, as in the case of existing marsupials. No one will pretend that so perfect a structure as the abnormal double uterus in ·woman could be the result of mere chance. But tho principle of reversion, by which longlost dormant structures are called back into existence, might serve as the guide for the full development of the organ, even after the lapse of an enormous interval of time. Professor Canestrini,S6 after discussing the foregoing and various analogous cases, arrives at the same conclusion as that just given. He adduces, as another instance, the malar bone, which, in some of the Quadrumana and other mammals, normally consists of two portions. This is its condition in the two-months-old human fcetus; and thus it sometimes remains, through :1.rrestecl development, in man when adult, more especially m the lower prognathous races. Hence Canestrini concludes that some ancient progenitor of man must have possessed this bone normally divided into two portions, which subsequently became fused together. In man the frontal bone consists of a single piece, but in the embryo and in children, and in almost all the lower 1~ammals, it consists of two pieces separated by a distmct suture. This suture occasionally persists, more or less distinctly, in man after maturity, and more fre- • 36 'Annun~io. d~lla Soc. dei Naturalisti in Modena,' 1867, p. 83. P1of .. canestnm gtves extracts on this subject from various authorities. ~aunllard re~arks, that as he has found a complete similarity in the form, proportiOns, and connexion of the two malar bones in several ln:man subjects .and in certain apes, he cannot consider this disposition of the parts as s1mply accidental. (;rrAP. IV. MANNER OF DEVELOPl\IENT. 125 quently in ancient than in recent crania, especially as Canestrini has observed in those exhumed from the Drift and belonging to the brachycephalic type. Here again he comes to 'the same conclusion as in the analoO'OUS case of the malar bones. In this and other in~tances presently to be given, the cause of ancient mces approaching the lower animals in certain characters more frequently than do the modern races, appears to be that the latter stand at a somewhat greater distance in the long line of descent from their early semi-human progenitors. Various other anomalies in man, more or less analogous with the foregoing, have been advanced by different authors 37 as cases of reversion; but these seem not a little doubtful, for we have to descend extremely low in the mammalian series before we find such structures normally present.3 B ar A whole series of cases is given by Isid. Geoffroy St.-Hilaire, 'Hist. des Anomalies,' tom. iii. p. 437. 38 In my' Variation of Animals under Domestication' (vol. ii. p. 57) I attributed the not very rare cases of supernumerary mammre in women to reversion. I was led to this as a probable conclusion, by the additional mammre being generally placed symmetrically on the breast, and more especially from one case, in which a single efficient mamma occurred in the inguinal region of a woman, the daughter of another woman with supernumerary mammre. But Prof. Preyer (' Der Kampf um das Dasein,' 1869, s. 45) states that mammm erraticle have been , known to occur in other situations, even on the back; so that the force of my argument is greatly weakened or perhaps quite destroyed. With much hesitation I, in the same work (vol. ii. p. 12), attributed the frequent cases of polydactylism in men to reversion. I was partly led to this through Prof. Owen's statement, tbat some of the Ichthyopterygia possess more than five digits, and therefore, as I supposed, hacl retained a primordial condition; but after reading Prof. Gegenbaur's paper(' Jenaischen Zeitschrift,' B. v. Heft 3, s. 3-!1), who is the highest authority in Europe on such a point, and who disputes Owen's conclusion, I see that it is extremely doubtful whether supernumerary digits can thus be accounted for. It was the fact that such digits not only frequently occur and are strongly inherited, but have the power of regrowth after amputation, like the normal digits of the lower verte- |