496 POPULAR SCIENCE MONTHLY. 



they are perfect, and retain, even after several generations, their orig- 

 inal characters. They originate with a shock or jump and then are 

 constant. 



They are formed from the mother species as side issues, and not 

 because the mother species undergoes a gradual change. On the con- 

 trary in nearly all mutations, the species continues unchanged, and 

 to it belongs the great mass of individuals, until one day the strug- 

 gle for life shall turn the scales. 



Mutability is not one-sided, as many paleontological series would 

 lead one to expect, but many-sided as must be deduced from the prin- 

 ciples laid down by Darwin. And the new Oenotheras vary in differ- 

 ent organs and in various directions; most frequently the new charac- 

 ters are injurious, sometimes indifferent, occasionally beneficial, prob- 

 ably at least. Next to strong new species there occur weak ones, next 

 to these, those so weak as never to reach the flowering period; and 

 finally sterile forms. From this array of forms nature, in the strug- 

 gle for life, later on makes its choice ; only those most fit continue to 

 exist. Even here experiment confirms theory. 



What is the duration of a mutation period? Geology answers: 

 probably very long, for otherwise the chances of life of the new species 

 would be too small. And it seems to me that in the case of Oenothera 

 Lamarckiana I have seen neither the beginning nor the end. The 

 fifteen years during which I studied the species comprises probably 

 but a very small part of that period. 



