CHANGE IN THE BAR GENE OF DROSOPHILA 



297 



how small can be definitely ascribed either to a particular ger- 

 minal or a particular environmental change, only a start has been 

 made. However, analysis of the one group of factors facilitates 

 the investigation of the other. All the material described in the 

 present paper is preserved in alcohol as far as possible and is 

 accessible for future reference. This explains the use of culture 

 numbers in the descriptions. 



ORIGIN, BEHAVIOR AND LOCATION OF BAR EYE 



As described by Tice ('14), bar-eye appeared in a single male 

 in a stock with full eyes. In one of my wild stocks, no. 345, full 



TABLE 1 



Comparison of full eye, bar, and ultra-bar, at 27°C. Females. The class distribu- 

 tions in the same populations are given in table 3 and figure 2 



* With the small number of cases represented under full eye, the standard 

 deviation and probable error determinations of course have no great significance. 

 The values given are those obtained by following the usual methods employed 

 when larger numbers of cases are available. They may, however, indicate in a 

 very general way the probable variability of the stock as compared with the 

 others. 



2 Second low selected generation including all matings. 



' A factorial unit is one that produces a 10 per cent change in facet number. 



^According to the method used, standard deviation is directly a measure of 

 variability and may be used as a coefficient of factorial variability. 



