486 POPULAR SCIENCE MONTHLY 



American species produced by Mr. Burbank, have been in past years 

 sold in the cities of Germany. In any event, we have as yet no reason 

 to assume that the various mutants of the evening primrose are in any 

 sense comparable to the wild species of the same group now existing 

 in America. 



While saltation remains as one of the probable sources of specific 

 difference, its actual relation to the process of species-forming in nature 

 is yet to be proved. 



Dr. de Yries's assertion that the process of natural selection is 

 mainly a conflict between saltatory offshoots and not a competition be- 

 tween similar individuals (' intraspecific instead of interspecific com- 

 petition') is hardly justified by the facts. The real conflict is that 

 of the individuals maintaining life against the pressure of external 

 conditions. 



In the struggle for existence, each individual survives which can. 

 The close presence of other similar individuals and that of unlike in- 

 dividuals are alike parts of the environment which each individual 

 that leaves progeny has in some degree succeeded in conquering. This 

 conquest takes place through adaptation to the actual conditions, con- 

 cession to the actual environment. 



It is highly probable that saltations in general are of the same 

 nature as fluctuations, and that they occur in nature far more com- 

 monly than has been supposed. Unless in some way protected by 

 isolation, the traits thus developed are likely to be swamped and lost 

 by interbreeding with the mass. But it is conceivable that they are 

 not always thus lost, as a very favorable variation may overwhelm the 

 mass. But it is also clear that isolation of some sort would be usually, 

 if not always, essential to any survival of a group possessing saltatory 

 characters. 



Hybridization 



In crossing related species, new forms arise, having in part a blend 

 or a mosaic of the characters of the two parent species, in part other 

 traits or characters, the origin of which may not be clearly traced. 

 Usually the second generation shows a great range of variation, often 

 deviating farther in some respects from the average type than was the 

 case with either of the original parents. The progeny of these variants 

 may also vary widely. It has been sought to define the laws govern- 

 ing these variations. When only a few easily recognized characters are 

 concerned, it has been possible to trace a certain regularity, conforming 

 in general to the Mendelian law. But different species differ not in 

 one way, but in a thousand ways. These traits are so interwoven and 

 so variously related, some of them cumulative and some contradictory, 

 that in most cases no law determining which characters shall be domi- 

 nant in each case and which recessive can be made out. While the 



