THE DETERMINATION OF DOMINANCE. 315 



The huge preponderance of this complex type, which was 

 neither one nor the other of the three species, suggests at once, 

 of course, that the results could not be due to any selective 

 process, because the type was not one of the original types but 

 a hybrid complex which was preserved because of its fitness for 

 the location in which it was living. 



The wintering condition of 1 906-1 907 were especially rigorous, 

 at least as judged by the number of beetles that I found in that 

 location in 1906-07, when the following census was made: 



This shows that during the winter practically only the hybrid 

 combination was able to survive. These reproduced and gave 

 a progeny late in July, 1907. An inspection was made early 

 in August when I found only the dominant type present in the 

 fifth hybrid generation. 



The culture was not seen again until the spring of 1908, when a 

 considerable number of the dominant form of the sixth hybrid 

 generation was found emerging. These were taken to Chicago 

 and subjected to analytical experiments and were found to breed 

 true, both in group and in pedigreed cultures, with this exception, 

 that in both group and pedigreed cultures, there occurred 

 from time to time sporadic variants often standing a con- 

 siderable distance apart from the rest of the population, which, 

 when inbred, either with sports like themselves, or back to the 

 parent type, gave behaviors which in every way are comparable to 

 the behavior observed in many of the forms which are supposed 

 to have arisen by a mutative process. These strains were kept 

 through the years 1908 and 1909, and gave results which strongly 

 suggested that the interpretation of a mutative period, as de- 



