194 Darwin, and after Darwin. 



species. And the highly peculiar characters which 

 they present conform to all "the most essential 

 features of specific characters," as these are stated 

 by Mr. Wallace in his objection to the case of the 

 pig's appendages. That is to say, "they are sym- 

 metrical, they are inherited, and they are constant." 

 In point of fact, they are always " constant," both as 

 to occurrence and symmetry, while they are so 

 completely " inherited " that not only does " a niata 

 bull and cow invariably produce niata calves " ; but 

 even when crossed with other cattle the result is a 

 hybrid, " with the niata character strongly displayed." 



Hence, if we were to follow Mr. Wallace's criteria 

 of specific characters, which show that the pig's 

 appendages "cannot be classed with specific char- 

 acters" (or with anything of the nature of specific 

 characters), it would follow that the niata peculiarities 

 can be so classed. This, therefore, is a case where 

 he will find all the reasons which in other cases 

 he takes to justify him in falling back upon the 

 argument from ignorance. The cattle are half 

 wild, he may urge ; and so the three- fold con- 

 stancy of their peculiar characters may very well 

 be due, either directly or indirectly, to natural 

 selection i.e. they may either be of some hidden 

 use themselves, or correlated with some other modi- 

 fications that are of use : it is, he may say, as in 

 such cases he often does say, for us to disprove both 

 these possibilities. 



Well, here we have one of those rare cases where 

 historical information, or other accidents, admit of 

 our discharging this burden of proving a negative. 

 Darwin's further description shows that this custom- 



