io6 



CHARLES ZELENY. 



value is 1.080. In other words, one degree decrease in tempera- 

 ture between 30 ° and 15 ° causes an average increase of 8 per cent, 

 in ommatidial number. Between 27 and 15 the average increase 

 is 7.6 per cent. 



F 



B 



H 



FU 



U 



Fig. 1. F, full eye. B, bar. U, ultra-bar. Hj,y, heterozygote of full 

 and bar. Hjrp, heterozygote of full and ultra-bar. 



In some work not yet published, but which she has allowed me 

 *to use for the present purpose, Miss Karrer finds that full eye has 

 an average increase of only about 2^2 per cent, per degree between 

 29 and 15 °. 



Table I. 



Number of Ommatidia. 



Two full eye factors. Homozygous 



full eye 



One full eye and one ultra-bar factor. 



Heterozygote 



Two ultra-bar factors. Homozygous 



ultra-bar , 



Difference between heterozygote and 



homozygous ultra- bar 



