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Show 4 INITERITANCE. CnAr. :XII. detail of structure. But inheritance is not certain; for if it were, the breeder's art 4 would be reduced to a certainty, and there would be little scope left for all that skill and perseverance shown by the men who have left an enduring monument of their success in the present state of our domesticated animals. It is hardly possible, within a moderate compass, to impress on the mind of those ·who have not attended to the subject, tho full conviction of the force of inheritance which is slowly acquired l,y rearing animal8, by studying tho many treati ses whic:h lHwo h 'en puulished on tho yarions domo~tic m1imals, an<l by ronycr;-; ing "\Yith brcoclcrs. I will select a few facts of tho bnd, which, as far DS I can jmlge, have most inftnenced my own mi ucl. ' Vith man ancl tho domestic animals, certain peculiarities have appeared in an indiviclunl, at rare intervals, or only onco or t\\'ice in tho history of tho worlcl, but have reappeared in several of tho children and grandchildren. Thus I~ttmbert, "the porcupineman,'' whose skin was thickly covered with warty projections, ·which ..w ore periodically moulted, had all his six children and two grandsons similarly affected.5 The face and body being covered with long hair, accompanied by deficient teeth (to which I shall hereafter refer), occurred in three successive generations in a Siamese family; but this case is not unique, as a woman6 with a completely hairy face was exhibited in London in 1GG3, and another instance has recently occurred. Colonel Hallam 7 has described a race of two-legged pigs, ''the hinder extremities being entirely wanting;" and this deficiency was transmitted through three generations. In fact, all races presenting any remarkable peculiarity, such as solid-hoofed swine, 1\Iauchamp sheep, niata cattle, &c., are instances of the longcontinued inheritance of rare deviations of structure. ""When we reflect that certain extraordinary peculiarities have 4 'The Stud Farm,' by Cecil, p. 39. 5 \Philosophical Transactions,' 17 55, p. 23. I have seen only sccon<l-ll:1.nd accounts of the two grandsons. 1\Tr. Seclgwick, in a paper to which I sb}l,U herea fter often refm·, states that four gl·nerations were rdfecteu, and iu each the males alone. 6 Barbara \'an Beck, figured, as I am informed by the Rev. W. D. Fox, in Woodburn's ' Gallery of Rare Portraits.' 181G, vol. ii. 7 'Proc. Zoolog. Soc.,' 1833, p. lG. CHAP. XII. INHERITANCE. 5 thus app?ared in a single individual out of many millions, all exposed m the same country to the same general conditions of life~ and, again, that the same extraordinary peculiarity has sometimes appeared in indiviCluals living under widely different c?~ditions of li~e, we are driven to conclude that such peculianiles are not du·ectly due to the action of the surroundinO' conditions, but to unknown laws acting on the organisati~n or constitution of the individual ;-that their production stands in hardly closer re1ation to the conditions than does life itself. If this be so, and the occurrence of the same unusual character in the child and parent cannot be attributed to both having been exposed to tho same unusual conditions, then the followin()' problem is worth consideration, as 'shmYing that the resul~ cannot be due, as some authors have supposed, to mere coincidence, but must be consequent on the members of the same famil! inheriting something in common in their constitution. Let ~t be assumed that, in a large population, a particulal' affectiOn occurs on an average in one out of a million so that the a priori chance that an individual taken at rancloru '~ill be s~ affoct~d is ~n~y one in a million. Let the population cons1st of s1xty m1lhons, composed, we will assume of ton million fi:t1~ilics, each containing six members. On the~ dab, Professor Stokes bas calculated for me that the odds will bo no less than 8333 millions to 1 that in t.he ten million fc.tmilios there will ~ot be even a single family in which one parent a~1cl two children \Yill be affected Ly the peculiarity in questw. n. Dut numerous cases could be given, in \Yhich several children hl~Ye been affected by the same rare peculiarity "\Yith one of ~hen· pare~ts; and in this case, more especially if the grcwdchi.ldr.en be mcludcd in the calculation, the oclcls againt5t mere comcic.lonco become something prodigious, almost beyo11cl enumeration. . In some respects the evidence of inheritance is more strikinr'· when we consider tho Tcappea.nmce of triflinrr peculiarities. D~ n d t · · o 1 . o g ~1~11ormorly told me of an English family in which, for many• generatiOns, some memb~rs hnc.l a single lock differently colonre~l from the. rest ~f the h~nr. I knew an Irish gentleman, who, o~ the n ght s1cle of h1s head, hncl a small white Jock in tho 1mdst of his dark hair: he assured me that his grandmother had |
