BLASTOGENIC VARIATIONS. 139 



breeders and others, who seldom troubled to substan- 

 tiate their views by measurements and figures. 



The phenomenon of Reversion or Atavism has long 

 been recognised, not only by agriculturalists and 

 breeders, but also by others who have witnessed its oc- 

 currence in members of the human race. One of the 

 simplest instances of reversion is that of a child or a 

 lower animal resembling a grandparent more closely 

 than its immediate parents. Much more remarkable, 

 however, are those instances in which the resemblance 

 is to a remote ancestor, or to some distant member in a 

 collateral line (supposing, of course, that these be held 

 to be properly substantiated). Cases of reversion are 

 very frequent in respect of secondary sexual characters, 

 as when a son resembles his maternal grandsire more 

 closely than his paternal in some such attribute as a 

 peculiarity of the beard, in the case of man; of the 

 horns, in the case of the bull; and of the hackles or 

 comb in the cock. Also it is well known that certain 

 diseases, such as haemophilia and colour-blindness, are 

 frequently transmitted to male offspring through a 

 woman who herself remains unaffected. 



For most of our knowledge on the subject of rever- 

 sion we are indebted to the labours o Charles Darwin, 

 who obtained most valuable experimental evidence him- 

 self, besides collecting from most varied sources the re- 

 sults obtained by others. One of the most striking in- 

 stances he records is that of a pointer bitch,* which pro- 

 duced seven puppies. Four of these were marked with 

 blue and white, which is so unusual a colour with 

 pointers that the animal was thought to have played 

 * " Animals and Plants," ii. p. 8. 



