Modification of Germinal Constitution of Organisms 185 



showing again a marked decrease in the undecimlineata 

 form, a lesser decrease in the intermediate hybrid type, and 

 a much greater relative increase in the signaticollis type. 

 These hibernated during the winter of 1905-6 and emerged 

 in June, 1906. They were allowed to interbreed freely. 

 The population was not seen at the time of emergence, 

 but in the fourth generation it was observed in July, 1906, 

 and the undecimlineata t^pe and the mid- type were nearly 

 absent. The census made at this time, when the first 

 generation of the year was apparently at its height, ga\'e the 

 following results: 



SignalkoUis Type Mid-Type Undecimlineata Type 



3-275 45 7 



These then inbred and the colony was next seen in Septem- 

 ber at about the middle of the month, when the census of the 

 individuals in the colony was as follows in Generation V : 



Signaticollis Type Mid-Type Undecimlineata Type 



1.823 6 o 



These hibernated during the winter of 1906-7 and emerged 

 in June, 1907, reproduced at once, and gave an abundant 

 progeny which emerged as Generation VI between the loth 

 and 25th of July. These when seriated gave the following 

 results : 



Signaticollis Type Mid-Type Undecimlineata Type 



2,255 2 O 



The second generation of 1907 emerged late in August 

 and early in September, and of this generation the undecim- 

 lineata type was entirely absent, and the mid-t>pe prac- 

 tically so. These hibernated and when seen in the spring 

 of 1908 only the signaticollis t>'pe emerged. Both genera- 

 tions of 1908 and both generations of 1909 have developed 

 the presence of the signaticollis type only. 



