Chap. XIV. SUMMARY. 59 



has been lost through variation, it occasionally reappears 

 through reversion, so that the parents apparently fail to 

 transmit tlieir own likeness. In all cases, however, we may 

 safely conclude that the child inherits all its characters from 

 its parents, in whom certain characters are latent, like the 

 secondary sexual characters of one sex in the other. When, 

 after a long succession of bud-generatious, a floAver or fruit 

 becomes separated into distinct segments, having the colours 

 or other attributes of both parent-forms, we cannot doubt 

 that these characters were latent in the earlier buds, though 

 they could not then be detected, or could be detected only in 

 an intimate] 3^ commingled state. So it is with animals of 

 crossed jDarentage, w^hich with advancing years occasionally 

 exhibit characters derived from one of their two parents, of 

 which not a trace could at first be perceived. Certain mon- 

 strosities, which resemble what naturalists call the typical 

 form of the grouj) in question, apparently come under the 

 same law of reversion. It is assuredly an astonishing fact 

 that the male and female sexual elements, that buds, and 

 even full-gro\\Ti animals, should retain characters, dnring 

 several generations in the case of crossed breeds, and during 

 thousands of generations in the case of pure breeds, written 

 as it were in invisible ink, yet read}^ at any time to be evolved 

 under certain conditions. 



What these conditions precisely are, we do not know. 

 But any cause which disturbs the organisation or constitu- 

 tion seems to be sufficient. A cross certainly gives a strong 

 tendency to the reappearance of long-lost characters, borli 

 corporeal and mental. In the case of plants, this tendency 

 is much stronger with those species which have been crossed 

 after long cultivation and which therefore have had their 

 constitutions disturbed by this cause as well as by cro. sing, 

 than with species which have always lived under their natural 

 conditions and have then been crossed. A return, also, of 

 domesticated animals and cultivated plants to a wild state 

 favours reversion ; but the tendency under these circumstances 

 has been much exaggerated. 



When individuals of the same family which differ some- 

 what, and when races or species are crossed, the one is often 



