264 ^ag &enrum, <ssaj)S, anb Ij^hwfag. [xn. 



should attempt to apply it in Nature would soon find 

 himself involved in great, if not inextricable, difficulties. 

 As we have said, it is indubitable that offspring tend to 

 resemble the parental organism, but it is equally true 

 that the similarity attained never amounts to identity, 

 either in form or in structure. There is always a certain 

 amount of deviation, not only from the precise characters 

 of a single parent, but when, as in most animals and 

 many plants, the sexes are lodged in distinct individuals, 

 from an exact mean between the two parents. And 

 indeed, on general principles, this slight deviation seems 

 as intelligible as the general similarity, if we reflect how 

 complex the co-operating "bundles of forces" are, and 

 how improbable it is that, in any case, their true re- 

 sultant shall coincide with any mean between the more 

 obvious characters of the two parents. Whatever be 

 its cause, however, the co-existence of this tendency to 

 minor variation with the tendency to general similarity, 

 is of vast importance in its bearing on the question of 

 the origin of species. 



As a general rule, the extent to which an offspring 

 differs from its parent is slight enough ; but, occasionally, 

 the amount of difference is much more strongly marked, 

 and then the divergent offspring receives the name of a 

 Variety. Multitudes, of what there is every reason to 

 believe are such varieties, are known, but the origin of 

 very few has been accurately recorded, and of these we 

 will select two as more especially illustrative of the main 

 features of variation. The first of them is that of the 

 " Ancon," or " Otter" sheep, of which a careful account 

 is given by Colonel David Humphreys, F.K.S., in a letter 

 to Sir Joseph Banks, published in the Philosophical 

 Transactions for 1813. It appears that one Seth Wright, 

 the proprietor of a farm on the banks of the Charles 

 River, in Massachusetts, possessed a flock of fifteen ewes 



