V.] SPECIFIC STABILITY. 139 



to " the greater frequency of a monster proboscis in the 

 pig than in any other animal." But with the exception of 

 the peculiar muzzle of the Saiga (or European Antelope), 

 the only known proboscidian Ungulates are the elephants 

 and tapirs, and to neither of these has the pig any close 

 affinity. It is rather in the horse than in the pig that we 

 might look for the appearance of a reversionary proboscis, 

 as both the elephants and the tapirs have the toes of the 

 hind foot of an odd number. It is true that the elephants 

 are generally considered to form a group apart from both 

 the odd and the even-toed Ungulata. But of the two, their 

 affinities with the odd-toed division are more marked. 1 



Another argument in favour of the, at least intermitting, 

 constancy of specific forms and of sudden modification, may 

 be drawn from the absence of minute transitional forms, 

 but this will be considered in the next chapter. 



It remains now to notice in favour of specific stability, 

 that the objection based upon the physiological difference 

 between " species " and " races " still exists unrefuted. 



Mr. Darwin freely admits difficulties regarding the 

 sterility of different species when crossed, and shows satis- 

 factorily that it could never have arisen from the action 

 of " Natural Selection." He remarks 2 also : " With some 

 few exceptions in the case of plants, domesticated varieties, 

 such as those of the dog, fowl, pigeon, several fruit trees, 

 and culinary vegetables, w r hich differ from each other in 

 external characters more than many species, are perfectly 

 fertile when crossed, or even fertile in excess, whilst 



1 This lias been shown by my late friend, Mr. H. N. Turner, jun., in an 

 excellent paper by him in the ' ' Proceedings of the Zoological Society for 

 1849," p. 147. The untimely death, through a dissecting wound, of this 

 promising young naturalist, was a great loss to zoological science. 



2 "Animals and Plants under Domestication," vol. ii. p. 189. 



