348 DARWINISM TO-DAY. 



however, only as weak young plants that rarely flowered. 

 Five of the new forms were seen either in the Hilversum 

 field, or else raised from seeds that had been collected there. 

 These facts show -that the new species are not due to culti- 

 vation, and that they arise year after year from the seeds 

 of the parent form, O. laniarckiana." 



Since the publication of de Vries's theory and the data 

 and considerations on which it is based (these considera- 

 tions including an unusually keen and effective 

 Attitude of ., . . r ^ ^ . . r r 



naturalists to- criticism of the Darwinian factors of species- 

 ward the muta- forming) a great deal of discussion of the 



tious theory ( 



theory has been indulged in. On the whole 

 the theory has been warmly welcomed as the most promis- 

 ing way yet presented 22 out of the difficulties into which 

 biologists had fallen in their attempts to explain satisfactorily 

 the phenomena of the origin of species through Darwinian 

 selection. And especially has been welcomed the fruitful idea 

 of unit species characters, and of the indivisibility and the 

 distinctness of such characters in inheritance. But with all 

 the interest aroused by de Vries's presentation of his theory, 

 and with all the. eager scrutiny of species and records of 

 species-appearing an output of new evidence amazingly 

 small (when one stops to consider the publicity gained for 

 the theory itself and its obvious need of more confirmatory 

 data of observation and experiment) has resulted. Even 

 though the answer may be that experiment takes time, the 

 lack of new observational evidence of the occurrence of 

 mutations, 23 and of the origin of new species through muta- 

 tions in nature, is significant. It is my belief that a reaction 

 against the curiously swift and widespread partial to com- 

 plete acceptance of the mutation theory as the sufficient "way 

 out" of our troubles to explain the origin of new species will 

 soon occur. ( See notes 24, 25, and 26, the appendix of this 

 chapter, for references to certain recent criticisms of the 

 mutation theory.) 



