INHERITANCE 103 



isolated parts of even the highest animals may 

 retain their vitality and special properties when 

 placed under favourable conditions, More striking 

 examples are afforded by such cases as those 

 quoted by Mr. Darwin : in one instance, the spur 

 of a cock inserted into the ear of an ox lived for 

 eight years, and grew to a length of nine inches ; 

 while in another, the tail of a pig removed from its 

 natural position and grafted into the middle of the 

 animal's back lived for a time and recovered 

 sensibility. 



The phenomena of Reversion are again of great 

 importance in reference to the problem of Inherit- 

 ance. It is well known that animals may trans- 

 mit to their offspring characters which are not 

 manifested in themselves : the tendency of gout 

 and some other diseases to appear in alternate 

 generations is perhaps the most familiar instance. 

 In such cases we must regard the disease, or other 

 peculiarity, as present in a latent form in the 

 generations which it apparently skips, for how 

 otherwise could we understand its reappearance in 

 a later generation ? The tendency of domestic 

 animals, and more especially of cultivated flowers 

 and fruits, to revert either in form, colour, or 

 other characteristics to the ancestral wild con- 

 dition, is another good illustration of what may 

 well be termed Latent Inheritance. Readers of 

 Mr. Darwin's works will call to mind his famous 

 experiments on pigeons ; more especially that 

 crucial one in which he first paired a black Barb 

 with a red Spot ; then another black Barb with a 



