Origin of Peloric Toadflax 461 



the whole period of its existence it remains the 

 same, at the end as sharply defined from its 

 nearest allies as in the beginning. Should 

 some of the units die out, the gaps between the 

 neighboring ones will become wider, as must 

 often have been the case. Such segregations, 

 however important and useful for systematical 

 distinctions, are evidently only of secondary 

 value, when considering the real nature of the 

 units themselves. 



We may now take up the other side of the 

 problem. The question arises as to how species 

 and varieties have originated. According to 

 the Darwinian theory they have been produced 

 from one another, the more highly differenti- 

 ated ones from the simpler, in a graduated 

 series from the most simple forms to the most 

 complicated and most highly organized exist- 

 ing types. This evolution of course must have 

 been regular and continuous, diverging from 

 time to time into new directions, and linking 

 all organisms together into one common pedi- 

 gree. All lacunae in our present system are ex- 

 plained by Darwin as due to the extinction of 

 forms, which previously filled them. 



Since Lamarck first propounded the concep- 

 tion of a common origin for all living beings, 

 much has been done to clear up our ideas as to 

 the real nature of this process. The broader 



