Vol.. 7, 1921 
GENETICS: C. B. BRIDGES 
189 
less in presence of Diminished is thus 98.7%. The mortality of simple eye- 
less is usually not greater than 5%, and the mortality of the simple Di- 
minished is, as seen, about 47%. The mortality of Diminished-bent was 
even higher, viz. 99.5%, since only 9 Diminished-bents (males) hatched 
for 1727 wild-type sibs. 
Since mortality changes must necessarily be only consequences of so- 
matic changes, the exaggeration of the mortality of the Diminished com- 
pounds is another evidence of exaggeration of somatic changes — probably 
of the internal anatomy in addition to the observed superficial changes. 
The mortality of Diminished, and of the Diminished compounds, is 
mainly due to somatic changes in the pupa stage: (a) If the mortality of 
Diminished individuals were due to changes in the larvae, then mass- 
cultures, because of the greater competition among the too numerous 
larvae, should show a lower proportion of Diminished than do sister pair 
cultures, but this was found not to be the case, (b) Examination of the 
culture bottles of the crosses of Diminished by eyeless showed that the 
number of Diminished-eyeless individuals that pupated but perished sub- 
sequently is approximately the same as the number of not-diminished 
flies that hatch. 
(12) Exaggeration of certain mutants outside the affected region: 
Diminished exaggerates the third-chromosome dominant Hairless, and to 
a slight extent certain other mutants. 
(13) Recurrent nature: Diminished has arisen independently at various 
times (see section II (1) below). 
II. All the above features of Diminished, including exaggeration (10, 
11, 12), are explainable by the theory of deficiency, and for nearly all 
there have been parallels in previously known cases of deficiency. Two 
features of Diminished appeared that made a sectional deficiency hypoth- 
esis inadequate. 
(1) High frequency of re-occurrence: Diminished has been recorded 
some twenty-five times within the space of a year, which is too high a fre- 
quency to be explained without extreme difficulty on the sectional de- 
ficiency view. Notch-deficiencies have been recorded some 18 times, 
but this was in a period extending over eight years. Furthermore, there 
is evidence that the different Notches are not re-occurrences of the same 
deficiency, but show character differences and involve sections that are dif- 
ferent in extent, though all possessing a common section in the neighbor- 
hood of facet. The different Diminished strains, on the oteher hand, are 
apparently identical. Most of the tests of this paper were carried out 
in parallel with strains No. 3, 4, 8, 15, and 3x. 
(2) Exceptions to normal inheritance: In a cross of Diminished to 
bent there appeared a single Diminished male that was not bent. This 
exceptional male was tested and was found not to carry bent, although 
