THE CREATION OF SPECIES 



A certain measure of success has attended these 

 experiments. For example, Dr. D. T. MacDougal 

 has treated the ovaries of the evening primrose 

 flower with various chemicals, and the seeds from 

 flowers thus treated sometimes produce plants en- 

 tirely different from the mother plant. Professor 

 C. S. Gager has gained corresponding results by 

 treating the pollen of plants with radium. Professor 

 T. H. Morgan has similarly subjected the eggs of a 

 certain fly called Drosophila to the influence of ra- 

 dium, and has produced individuals differing in 

 some striking respects from their parents. One, for 

 example, had very short wings, and it was found that 

 these short-winged mutants bred true for successive 

 generations. 



Professor Jacques Loeb, in association with Mr. 

 F. W. Bancroft, has experimented with the same 

 species of fly, to see what effect might be pro- 

 duced by subjecting the insect to high temperature. 

 The flies were bred in a thermostat, the temperature 

 of which was kept constant within one degree of 30.5 

 degrees Centigrade. Under these circumstances, in 

 the fifth generation a number of dark flies appeared, 

 and it was found that this dark variety constituted 

 a permanent race. Subsequent experiments, how- 

 ever, showed that the influence of temperature did 

 not necessarily produce dark mutants. Experiments 

 with radium were also somewhat indeterminate, 

 although divergent forms dark races, pink-eyed, 

 white-eyed, and short-winged forms were some- 

 times produced. 



Professor W. L. Tower, in experiments with bee- 

 13 185 



