An Analysis of the Bristle Forming Reactions in Drosophila Melanogaster Scute-1.

( I ~ I ) , PLUNKETT (1926), STANLEY (1932), and HARNLY (1932, 1936). Some of these workers have attempted to explain the mechanism of the temperature effect by the form of the curves obtained when the values of the measured character are plotted against the time of transfer. It is significant that the form of these curves, in all cases, appears to be sigmoid, resembling to some extent the probability integral curve. CHILD (1935b) and MARGOLIS (1935) have suggested that the form of these curves for the bristles of scute-1 and the facets of Bar eye, respectively, may be determined chiefly by the distribution in time of the TEP in the individual flies. In other words larvae hatching from eggs laid a t the same time do not all develop at the same rate and hence enter their individualTEP’s at different times. The TEP of the population (P) is the summation of two factors I) the variation (V) among the larvae in time of entering the T E P and 2 ) the duration (D) of the TEP in the individual flies, P = V + D . It was shown that V could be represented by a normal frequency distribution. In this paper the data are analyzed further to obtain the curves and equations of the developmental process leading to bristle number determination in scute-I. Using these equations and the curve of the probability integral i t is further possible to calculate the P curve. (I915), KRAFKA (I924), DRIVER (I93I), E. DRIVER (1925, I93I), LUCE