hS INHERITANCE Chap. XIV. 



being able to assign any cause, that, when a new character 

 appears, it is occasionally from the first constant, or fluctuates 

 much, or wholly fails to be transmitted. So it is with the 

 aggregate of slight differences which characterise a new 

 variety, for some propagate their kind from the first much 

 truer than others. Even with plants multiplied by bulbs, 

 layers, &c, which may in one sense be said to form parts of 

 the same individual, it is well known that certain varieties 

 retain and transmit through successive bud-generations their 

 newly-acquired characters more truly than others. In none 

 of these, nor in the following cases, does there appear to be 

 any relation between the force with which a character is 

 transmitted and the length of time during which it has been 

 transmitted. Some varieties, such as white and yellow hya- 

 cinths and white sweet-peas, transmit their colours more 

 faithfully than do the varieties which have retained their 

 natural colour. In the Irish family, mentioned in the twelfth 

 chapter, the peculiar tortoiseshell-like colouring of the eyes 

 was transmitted far more faithfully than any ordinary colour. 

 Ancon and Mauchamp sheep and niata cattle, which are all 

 comparatively modern breeds, exhibit remarkably strong- 

 powers of inheritance. Many similar cases could be adduced. 

 As all domesticated animals and cultivated plants have 

 varied, and yet are descended from aboriginally wild forms, 

 which no doubt had retained the same character from an 

 immensely remote epoch, we see that scarcely any degree of 

 antiquity ensures a character being transmitted perfectly 

 true. In this case, however, it may be said that changed 

 conditions of life induce certain modifications, and not that 

 the power of inheritance fails; but in every case of failure, 

 some cause, either internal or external, must interfere. It 

 will generally be found that the organs or parts which in 

 our domesticated productions have varied, or which still 

 continue to vary, — that is, which fail to retain their former 

 state, — are the same with the parts which differ in the natural 

 species of the same genus. As, on the theory of descent with 

 modification, the species of the same genus have been modified 

 since they branched off from a common progenitor, it follows 

 that the characters by which the}" differ from one another 



