Chap. XV. OF UNIFORMITY OF CHARACTER. 87 



When distinct breeds are allowed to cross freely, the result 

 will be a heterogeneous body; for instance, the dogs in Para- 

 guay are far from uniform, and can no longer be affiliated to 

 their parent-races. 4 The character which a crossed body of 

 animals will ultimately assume must depend on several con- 

 tingencies, — namely, on the relative numbers of the individuals 

 belonging to the two or more races which are allowed to mingle ; 

 on the prepotency of one race over the other in the transmission 

 of character; and on the conditions of life to which they are 

 exposed. When two commingled breeds exist at first in nearly 

 equal numbers, the whole will sooner or later become intimately 

 blended, but not so soon, both breeds being equally favoured in 

 all respects, as might have been expected. The following cal- 

 culation 5 shows that this is the case: if a colony with an 

 equal number of black and white men were founded, and we 

 assume that they marry indiscriminately, are equally prolific, 

 and that one in thirty annually dies and is born ; then " in 65 

 " years the number of blacks, whites, and mulattoes would be 

 " equal. In 91 years the whites would be l-10th, the blacks 

 u l-10th, and the mulattoes, or people of intermediate degrees of 

 " colour, 8-10ths of the whole number. In three centuries not 

 ? l-100th part of the whites would exist." 



When one of two mingled races exceeds the other greatly in 

 number, the latter will soon be wholly, or almost wholly, absorbed 

 and lost. 6 Thus European pigs and dogs have been largely 

 introduced into the islands of the Pacific Ocean, and the native 

 races have been absorbed and lost in the course of about 

 fifty or sixty years; 7 but the imported races no doubt were 

 favoured. Eats may be considered as semi - domesticated 

 animals. Some snake-rats (Mus alexandrinus) escaped in the 

 Zoological Gardens of London, '•' and for a long time afterwards 

 •• the keepers frequently caught cross-bred rats, at first half-breds, 

 " afterwards with less and less of the character of the snake-rat, 

 46 till at length all traces of it disappeared. 8 On the other hand, 



4 Rengger, ' Saugethiere,' &c, s. 154. jeet, and ably discussed it. 



5 White, 'Regular Gradation in Man,' 7 Rev. D. Tyerman, and Bennett, 

 p. H6. 'Journal of Voyages,' 1821-1829, vol. 



c Dr. W. F. Edwards, in his ' Charac- i. p. 300. 

 teres Physiolog. des Races Humaines,' » Mr. S. J. Salter, ' Journal Linn. 



p. 24, first called attention to this sub- Soc.,' vol. vi. 1862, p. 71. 



