1 82 Heredity and Eugenics 



From the year 1904 onward I have been able to carry 

 out a number of suggestive experiments in the further effort 

 to produce a mutating race experimentally. 



EXPERIMENTS IN THE SYNTHESIS OF A MUTATING STEM RACE 



An extensive set of these experiments has been in 

 progress for some years, some of which have now developed 

 far enough to allow of rather definite statements. The 

 method employed has been to take species derived from 

 nature from some restricted locality, to keep close watch 

 upon w^hat goes on in this locality, and also to analyze the 

 composition of the species from this locality by cultures in 

 the laboratory. In this way, stocks of known character are 

 obtained from experiment, and also natural stocks whose 

 attributes are well known are developed in the type localities. 

 In the experiments in synthesis either pedigreed stocks from 

 the laboratory, or the stocks from nature, or both, are 

 placed in nature upon their food plant in isolated localities, 

 or in large cages, and allowed to breed as if the introduction 

 were a natural one. 



In 1904, an isolated area of about an acre upon the 

 southern slope of a barranca, near Cuernavaca, was planted 

 with food plants, upon which both L. signaticollis and L. 

 undecimlineata would feed. In July, 1904, this spot was 

 stocked with a culture of 210 specimens of L. signaticollis, 

 from a standard location about a mile and a half distant, 

 and 354 specimens of L. undecimlineata, obtained at El Hule, 

 on the banks of the Rio Papaloapan. The groups were 

 equally divided between the sexes, were young and vigor- 

 ous, immediately began breeding, and intercrossed freely. 

 Under experimental conditions these forms cross freely in 



