Latent Characters 223 



most widely known instance, although other 

 cases might easily be cited. 



For our special purpose we may take up 

 only the more simple cases that may be avail- 

 able for experimental work. The great lines of 

 evolution of whole families and even of genera 

 and of many larger species obviously lie outside 

 the limits of experimental observation. They 

 are the outcome of the history of the ancestors 

 of the present types, and a repetition of their 

 history is far beyond human powers. We must 

 limit ourselves to the most recent steps; to the 

 consideration of the smallest differences. But 

 it is obvious that these may be included under 

 the same heads as the larger and older ones. 

 For the larger grades are manifestly to be con- 

 sidered only as groups of smaller steps, going in 

 the same direction. 



Hence we conclude, that even the smallest 

 steps in the evolution of plants which we are 

 able to observe, may be divided into progres- 

 sive, retrogressive and degressive ones. The 

 acquisition of a single new quality is the most 

 simple step in the progressive line, the becom- 

 ing latent and the reactivating of this same 

 quality are the prototypes of the two other 

 classes. 



Having taken this theoretical point of view, 

 it remains to inquire, how it concurs with the 



