In the F_2, from a cross of a double recessive (white vermilion) female by a triple recessive (eosin vermilion pink) male, there appeared, July 21, 1912, three white-eyed females which had two small, symmetrically placed, black, granular masses upon the thorax. These "dots" appeared to be dried exudations from pores. It did not seem possible that such an effect could be inherited, but as this condition had never been observed before, it seemed worth while to mate the three females to their brothers. In the next generation about 1 per cent of the males were dotted. From these females and males a stock was made up which in subsequent generations showed from 10 to 50 per cent of dot. Selection seemed to have no effect upon the percentage of dot. Although the stock never showed more than 50 per cent of dot, yet it was found that the normal individuals from the stock threw about the same per cent as did those that were dotted, so that the stock was probably genetically pure. The number of males which showed the character was always much smaller than the number of dotted females; in the hatches which produced nearly 50 per cent of dot, nearly all the females but very few of the males were dotted. Quite often the character showed on only one side of the thorax. Since this character arose in an experiment involving several eye-colors an effort was made by crossing to wild and extracting to transfer the dot to flies normal in all other respects. This effort succeeded only partly, for a stock was obtained which differed from the wild type only in that it bore dot (about 30 per cent) and in that the eyes were vermilion. Several attempts to get the dot separated from vermilion failed. Since this was only part of the preliminary routine work necessary to get a mutant stock in shape for exact experimentation, no extensive records were kept. LINKAGE OF VERMILION AND DOT. When a dot male with vermilion eyes was bred to a wild female the offspring were wild-type males and females. These inbred gave the data shown in table 19. TABLE 19.--_P_1 vermilion dot [male] x wild [female] [female]. F_1 wild-type [female] [female] x F_1 wild-type [male] [male]._ +------------+----------+-----------+-----------+-------------+---------+ | Reference. | F_2 | Wild-type | Vermilion | Vermilion | Dot | | | females. | [male]. | [male]. | dot [male]. | [male]. | +------------+----------+-----------+-----------+-------------+---------+ | 7 | 345 | 151 | 130 | 0 | 0 | | 8 | 524 | 245 | 220 | 3 | 0 | | +----------+-----------+-----------+-------------+---------+ | Total. | 869 | 396 | 350 | 3 | 0 | +------------+----------+-----------+-----------+-------------+---------+ {45}