THE LAWS OF VARIABILITY. 75 



or organs. Man can hardly select, or only with mnch 

 difficulty, any deviation of structure excepting such as 

 is externally visible ; and, indeed, he rarely cares for 

 what is internal. He can never act by selection, except- 

 ing on variations which are first given to him in some 

 slight degree by nature. No man would ever try to make 

 a fantail till he saw a pigeon with a tail developed in 

 some slight degree in an unusual manner, or a pouter till 

 he saw a pigeon with a crop of somewhat unusual size ; 

 and the more abnormal or unusual any character was 

 when it first appeared, the more likely it would be to 

 catch his attention. But to use such an expression as 

 trying to make a fantail is, I have no doubt, in most 

 cases, utterly incorrect. The man who first selected a 

 pigeon with a slightly larger tail, never dreamed what 

 the descendants of that pigeon would become through 

 long-continued, partly unconscious and partly methodi- 

 cal, selection. Perhaps the parent-bird of all fantails 

 had only fourteen tail-feathers somewhat expanded, like 

 the present Java fantail, or like individuals of other and 

 distinct breeds, in which as many as seventeen tail-feath- 

 ers have been counted. Perhaps the first pouter-pigeon 

 did not inflate its crop much more than the turbit now 

 does the upper part of its oesophagus — a habit which is 

 disregarded by all fanciers, as it is not one of the points 

 of the breed. 



DOUBTFUL SPECIES. 



Origin of The forms which possess in some consider- 



Species, aD ] e degree the character of species, but which 

 are so closely similar to other forms, or are so 

 closely linked to them by intermediate gradations, that 

 naturalists do not like to rank them as distinct species, 

 are in several respects the most important for us. We 



