Chap. XIII. EEVERSIOX. 81 



be a latent capacity and tendency to produce stripes, though 

 these may not appear once in a thousand generations ; that in 

 every white, black, or other coloured pigeon, which may have 

 transmitted its proper colour during centuries, there should 

 be a latent capacity in the plumage to become blue and to be 

 marked with certain characteristic bars ; that in every child 

 in a six-fingered family there should be the capacity for the 

 production of an additional digit ; and so in other cases. 

 Nevertheless, there is no more inherent improbability in this 

 being the case than in a useless and rudimentary organ, or even 

 in only a tendency to the production of a rudimentary organ, 

 being inherited during millions of generations, as- is well 

 known to occur with a multitude of organic beings. There is 

 no more inherent improbability in each domestic pig, during a 

 thousand generations, retaining the capacity and tendency to 

 develop great tusks under fitting conditions, than in the young 

 calf having retained for an indefinite number of generations 

 rudimentary incisor teeth, which never protrude through the 

 gums. 



I shall give at the end of the next chapter a summary of the 

 three preceding chapters ; but as isolated and striking cases 

 of reversion have here been chiefly insisted on, I wish to 

 guard the reader against supposing that reversion is due to 

 some rare or accidental combination of circumstances. When 

 a character, lost during hundreds of generations, suddenly 

 reappears, no doubt some such combination must occur ; but 

 reversions to the immediately preceding generations may be 

 constantly observed, at least, in the offspring of most unions. 

 This has been universally recognised in the case of hybrids 

 and mongrels, but it has been recognised simply from the 

 difference between the united forms rendering the resemblance 

 of the offspring to their grandparents or more remote pro- 

 genitors of easy detection. Eeversion is likewise almost in- 

 variably the rule, as Mr. Sedgwick has shown, with certain 

 diseases. Hence we must conclude that a tendency to this 

 peculiar form of transmission is an integral part of the 

 general law of inheritance. 



Monstrosities. — A large number of monstrous growths and 



