394 PROVISIONAL HYPOTHESIS Chap. XXVII. 



conditions of life due to confinement sometimes suffices to pre- 

 vent the development of masculine characters in male animals, 

 although their reproductive organs are not permanently 

 injured. In the many cases in M^hich masculine characters 

 are periodically renewed, these are latent at other seasons ; 

 inheritance as limited by sex and season being here com- 

 bined. Again, masculine characters generally lie dormant in 

 male animals until they arrive at the proper age for repro- 

 duction. The curious case formerly given of a Hen which 

 assumed the masculine characters, not of her own breed 

 but of a remote progenitor, illustrates the close connection 

 between latent sexual characters and ordinary reversion. 



With those animals and plants which habitually produce 

 several forms, as with certain butterflies described by Mr. 

 Wallace, in which three female forms and one male form 

 co-exist, or, as with the trimorphic species of Lythrum and 

 Oxalis, gemmules capable of reproducing these different forms 

 must be latent in each individual. 



Insects are occasionally produced vrith one side or one 

 quarter of their bodies like that of the male, with the other 

 half or three-quarters like that of the female. In such cases 

 the two sides are sometimes wonderfully different in structure, 

 and are separated from each other by a sharp line. As gem- 

 mules derived from every part are present in each individual 

 of both sexes, it must be the elective affinities of the nascent 

 cells which in these cases differ abnormally on the two sides 

 of the body. Almost the same principle comes into play 

 with those animals, for instance, certain gasteropods and 

 Verruca amongst cirripedes, which normally have the two 

 sides of the body constructed on a very different plan ; and 

 yet a nearly equal number of individuals have either side 

 modified in the same remarkable manner. 



Reversion, in the ordinary sense of the word, acts so inces- 

 santly, that it evidently forms an essential part of the 

 general law of inheritance. It occurs with beings, how^ever 

 propagated, whether by buds or seminal generation, and 

 sometimes may be observed with advancing age even in the 

 same individual. The tendency to reversion is often induced 

 by a change of conditions, and in the plainest manner b;y 



