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Show CHAP. XII. INHERITANCE. 24 . h me side. 62 In all such two sons were microphthalmdi c .o n ;tv h~w hs a t h e par.e nt has had an cases if truthfully reporte ' m ' h e child has been ' . d d more t an on organ injured on one 81 e, an d the same side, the chances born with the same organ affecte on But perhaps the most against mere com· c1' d en ce are enorm. ous. · by Dr. Brownw th fact IS that given remarkable and trustwor Y oung gum· eaw pi'gs inherited an 8equard/a namely, that many y b' h bad been subjected to . . d from parents w IC epileptiC ten ency . . . . the course of a few weeks a partw· u1 a r oper· ation. ' mdu.c mg m. d 't should be especi·a lly l · d' llye epilepsy · an 1 a convu sive 1sease 1 '- . 1 . . t physw . t b d a large number of OO'lS re no~ed t~at this em~nen which b;d not been operated on, and gumeawpigs from amm~£ls t d the epileptic tendency. On the no t one of these roam es 'ed d 'ttl'ng that m· J· un·e s an d mutl·- 1 ha ·dly avo1 a ID1 ' who e, we can. I £ ll d by disease, or perhaps exclu-lations, espeCially when ° owe . . .· d . when thus followed, are occaswnally mhente. . . slvely 't 1 monstrosities are mbented, of Although manyh conglemday been given and to which may h' h amples ave a rea ' . . w l~dde;a_' the lately recorded case of the transmissi~n ?urmg be f h . 1' with a cleft-palate in the wnter s own a century o are- 1P · b 't d • 64 t other malformations are rarely or never m en e . ~~:~~e ~:tter cases, many are probably due dto finjuri.esbin .tth~ d uld come under the hea 0 nonwm en e womb or egg, an wo f · . . . or· mutilations. With plants, a long catalogue o m-mJu. n eds t 't' of the most sen.o us an d d1' v ersi'f i ed na t ur e bente mons ros1 1es . could easily be given; and with plants, tbei~e IS ~o. ~~ason to suppose that monstrosities are caused by direct IDJUnes to the seed or ~mbryo. Causes of Non-inheritance. A large number of cases of non-inheritance are intellig~ble on the principle, that a strong tendency to inheritance does exist, but 62 This last case is quoted by Mr. Sed"'wick in 'British and Foreign Medico-Chirurg. Review,' April, 1861, p. 484. For Blumenbach, see abovew cited paper. See, also, Dr. P. L~cas, • Traite de l'Hered. Nat.,' tom. u. P· 492. Also 'Transact. Linn. Soc.,' vol. ix. p. 323. Some curious cases are given by Mr. Baker in' The Veterinary,' vo!· xiii. p. 7'l3. Another curious case ~ "'iven in the • Annales des Scienc. Nat., l t series, tom. xi. P· 324. 63 • Proc. Royal Soc.,' vol. x. P· 297. ....redi I 64 1\:U:. Sproule, in 'British •u ell Journal,' April18, 1863. CHAP. XII. INHERITANCE. 25 that it is overborne by hostile or unfavourable conditions of life. No one would expect that our improved pigs, if forced during several generations to travel about and root in the ground for their own subsistence, would transmit, as truly as they now do, their tendency to fatten, and their short muzzles and legs. Drayhorses assuredly would not long transmit their great size and massive limbs, if compelled to live on a cold, damp mountainous region ; we have indeed evidence of such deterioration in the horses which have run wild on the Falkland Islands. European dogs in India often fail to transmit their true character. Our sheep in tropical countries lose their wool in a few generations. There seems also to be a close relation between certain peculiar pastures and the inheritance of an enlarged tail in fat-tailed sheep, which form one of the most ancient breeds in the world. With plants, we have seen that the American varieties of maize lose their proper character in the course of two or three generations, when cultivated in Europe. Our cabbages, which here come so true by seed, cannot form heads in hot countries. Under changed circumstances, periodical habits of life soon fail to be transmitted, as the period of maturity in summer and winter wheat, barley, and vetches. So it is with animals ; for instance, a person whose statement I can trust, procured eggs of Aylesbury ducks from that town, where they are kept in houses and are reared as early as possible for the London market; the ducks bred from these eggs in a distant part of England, hatched their first brood on January 24th, whilst common ducks, kept in the same yard and treated in the same manner, did not hatch till the end of March ; and this shows that the period of hatching was inherited. But the grandchildren of these Aylesbury ducks completely lost their early habit of incubation, and· hatched their eggs at the same time with the common ducks of the same place. Many cases of non-inheritance apparently result from the conditions of life continually inducing fresh variability. We have seen that when the seeds of pears, plnms, apples, &c., are sown, the seedlings generally inherit some degree of family likeness from the parent-variety. Mingled with these seedlings, a few, and sometimes many, worthless, wild-looking plants commonly appear; and their appearance may be attributed to the principle of reversion. But scarcely a single seedling will be found |
