Abstract
1) Two environmental effects on the expressivity of Curly character were found and studied with Cy/l (2) 50c flies as material.
2) One of these effects was larval population density. It influenced Curly expressivity through the nutritional conditions of the larvae; the good nutritional conditions of the larval stage were observed to give typical Curly expression.
3) Another was cultural temperature; higher temperature gave higher expressivity of Curly character. The temperature-effective period was determined to be in the last one day of the pupal stage.
4) Within the range of these experiments the effect of temperature in the pupal stage was appeared to be more dominating than that of larval population density to determine Curly expressivity.
