The Philippine journal of science. [Vol. 67, no. 1]

67, 4

Clemente and Ong: New Glass-Eye Mutation

403

Thirteenth mutant, a male, found March 11, 1931, among
8 flies. Dark-eyed, big, strong, and vigorous. Mated to several morula female sibs. Eggs laid March 17, 1936, from which
the following were produced: 29 Red-eyed, 7 purple-eyed, and
2 dark glass-eyed females.
DESCRIPTION OF THE "NEW GLASS-EYE" MUTATION
This new mutation was called "glass eye" because of the
shiny surface of the eyes of the flies affected. The glassy
appearance is especially well manifested whenever bright light
falls on the surface of the eyes. The eyes are very much reduced in size, to about one-half that of normal. The reduction
is greatest on the anterior and posterior borders, thus making
the eyes appear spindle-shaped (Plate 1). There is a wide periphery of colorless area surrounding the eye as a result of the
reduction in size.
There are three shades of eye color among the glass-eyed
mutants. They are light, medium, and dark, but the most frequent is the dark (Plate 1). The color in all these shades is
uniformly distributed all over the eyes, unlike the glass eye of
Miller and of Mohr in which the color is unevenly distributed.
The different shades cannot be due to difference in age of the
flies, for all of the three shades were found even among the
newly emerged flies. Neither is the color different in the two
sexes as is true of the glass eye of Miller and of Mohr. The
difference in intensity of the color of glass eye is perhaps due
'to the interaction of genetic factors, such as orange eye, purple
eye, and red eye, which are present in the mutating stock. Our
unrecorded breeding observations seem to indicate that the dark
glass eye can produce all the three color shades; the medium
glass eye can produce both medium glass and light; whereas
the light glass eye can produce only light.
When seen under the microscope, the eyes are found to be
devoid of hairs on the surface, and instead of having facets
of hexagonal partitions as in normal eyes, they form a continuous single shiny mass very similar to glass. In other words,
the eyes are hairless and facetless, similar to the ocelli or
simple eyes of insects. Whether or not the ommatidia have
also lost their separate character is not known, for no serial
sections of the eyes have been made. There is no doubt but
that the absence of both the hair and facets are responsible for
giving the glassy or shiny appearance to the eyes.