JOSEPH KRAFKA, JR. 



419 



The Low Selected and the Unselected bar stocks parallel each other 

 closely in their temperature-facet relations. The Low Selected has a 

 consistently lower mean facet value for all temperatures studied. 



The Ultra-bar stock differs from the Low Selected first in the mean 

 facet values for all temperatures, and, second, in the amount of re- 

 duction for a degree Centigrade change in temperature. 



Facet 

 number 



15° 20° 25° 30° 



Tcmpemture 



Fig. 5. Temperature effect on the three bar stocks compared. The three curves 

 are all drawn to the same scale. The upper one is that of the Unselected bar 

 stock females, the middle that of the Low Selected bar stock females, and the 

 lower that of the Ultra-bar stock females. 



We may draw two conclusions from these curves: (1) The mean 

 facet number at any given temperature is not the same for all stocks. 

 (2) The difference in the mean number of facets between any two 

 temperatures is not a constant for all three stocks. In other words, 

 the number of facets is determined by a specific germinal constitution 

 plus a specific environment. 



