Modification of Germinal Constilution oj Organisms i8i 



There is not the least doubt as to the behavior of 0. 

 Lamarckiana and the appearance of the "mutants," and it 

 appeared to many that there was a good chance of producing 

 "mutating races" by external forces acting upon the germ 

 of the parent race. The last decade has produced a deal 

 of evidence that external forces can produce germinal 

 changes, but these are in all instances immediate and final. 

 New, divergent types, more or less separated from the 

 parent, have appeared, but in none are there subsequent 

 mutations. 



I had been at work upon this problem and had found 

 and reared sports of Leptinotarsa decemlineata as early as 

 1893, and on the appearance of DeVries' work I began in a 

 systematic way to try to produce mutating races by the 

 use of external forces. I have thus far positively failed to 

 produce a mutating race by these agencies, although I have 

 been able to get changes in profusion, some of which I shall 

 describe later. 



In 1 90 1 I tried to produce a mutating race by crossing 

 L. decemlineata, L. jimcta, and L. pallida, with the idea 

 that perhaps the interbreeding and combination of the 

 chief characters of the three into a hybrid complex would 

 produce a type which under changed conditions of 

 growth and development, or of changed or adverse 

 environment, would give the mutation behavior of 0. 

 Lamarckiana. The early experiments were just beginning 

 to show promise of interesting results when they were 

 brought to an end. As subsequent results have shown, this 

 was a good working h}^othesis but these first exi3eriments 

 would not have led to the results wanted. In 1902 Bateson 

 suggested that the mutation phenomena in Oenothera was 

 possibly akin to a Mendelian splitting of a hybrid t\pe. 



