PREPOTENCY IN CHARACTERS. 59 



a well-fixed character may defy for a time a change 

 of environment, or one, or even two or three " cross- 

 ings," yet it will assuredly disappear, should either of 

 these be persisted in. In the "Southdown" sheep, 

 for example, certain acquired characters have been 

 thus securely fixed; yet if we "cross" the "South- 

 down" with some other variety, the peculiar char- 

 acters of the former will soon be lost ; and similarly, 

 if the animals be transferred to an environment widely 

 differing from that in which their peculiar characters 

 were acquired, as, say, from the rich English pastures 

 to the bleak Welsh mountains, the animals will throw 

 off the acquired characters and revert to the original, 

 or acquire new characters altogether. 



It may be taken, therefore, that the longer any 

 character has "run in the family," the more deeply 

 is it rooted, so to speak, and the more difficult to 

 eradicate. And the character which has been handed 

 down through many generations is often so fixed and 

 dominant, that it will appear again and again in spite 

 of repeated " crossings " with fresh blood. Hence 

 the gravity of an hereditary disease is by no means 

 to be accurately measured by the symptoms presented 

 in the individual, but rather by the number of genera- 

 tions through which it has passed to reach him ; and 

 the risk of children inheriting such diseased condi- 

 tions or predisposition as lead to epilepsy, scrofula, 

 insanity, drunkenness and the like, will increase pro- 

 portionately with the number of generations through 

 which the tendency has been handed down. Thus, 



