36S PKOVISIONAL HYPOTHESIS Chap. XXVII. 



are often faithfully transmitted — frequently even when one 

 parent alone possesses some new peculiarity ; and we may 

 on the whole conclude that inheritance is the rule, and 

 non-inheritance the anomaly. In some instances a character 

 is not inherited, from the conditions of life being directly 

 opposed to its development; in many instances, from the 

 conditions incessantly inducing fresh variability, as with 

 grafted fruit-trees and highly-cultivated flowers. In the re- 

 maining cases the failure may be attributed to reversion, by 

 which the child resembles its grandparents or more remote 

 progenitors, instead of its parents. 



Inheritance is governed by various laws. Characters which 

 first appear at any particular age tend to reappear at a corre- 

 sponding age. They often become associated with certain 

 seasons of the year, and reappear in the offspring at a corre- 

 sponding season. If they appear rather late in life in one sex, 

 they tend to reappear exclusively in the same sex at the 

 same period of life. 



The principle of reversion, recently alluded to, is one of 

 the most wonderful of the attributes of Inheritance. It 

 proves to us that the transmission of a character and its 

 development, which ordinarily go together and thus escape 

 discrimination, are distinct powers ; and these powers in some 

 cases are even antagonistic, for each acts alternately in suc- 

 cessive generations. Reversion is not a rare event, depending 

 on some unusual or favourable combination of circumstances, 

 but occurs so regularly with crossed animals and plants, and 

 so frequently with uncrossed breeds, that it is evidently an 

 essential part of the principle of inheritance. We know that 

 changed conditions have the power of evoking long-lost 

 characters, as in the case of animals becoming feral. The 

 act of crossing in itself possesses this power in a high degree. 

 What can be more wonderful than that characters, which 

 have disappeared during scores, or hundreds, or even thou- 

 sands of generations, should suddenly reappear perfectly 

 developed, as in the case of pigeons and fowls, both when 

 purely bred and especially when crossed ; or as with the 

 zebrine stripes on dun-coloured horses, and other such cases ? 

 Many monstrosities come under this same head, as when 



