330 E. J. ALLEN AND E. W. SEXTON, 
ones, | male and 2 females, and 25 young. The white pigment in the 
eyes of both the large females was very much reduced. Twenty-three 
of the young were black-eyed, half-grown animals, with normal extra- 
retinal pigment and 2 very small ones, just extruded, one of which had 
no-white eyes. 
(3) A number of the animals brought in on February 11, 1915, were 
examined and all had normal eyes. They were kept together in one large 
bell jar, which was not examined until April 5, 1916. The bell-jar then 
contained 20 animals, all having black eyes with the white normal, 
excepting in one instance. This was a young animal and there was so 
little white pigment in the eyes that it required examination with the 
microscope (1 inch) to detect it. 
For another instance of the independent origin of no-white eyes 
see p. 336. 
SECTION IV. THE COLOURLESS EYE. 
CROSS BETWEEN COLOURED NO-WHITE AND ALBINO 
(Plate VI). 
The “albino” eye shows neither black nor red retinal pigment, and 
is regular and imperfect in shape, the ommatidia being few in number 
and unequal in size. The ‘ coloured no-white ” eye lacks only the white 
extra-retinal pigment, the black or red pigment, as well as the shape of 
the eye, the number, the size, and the arrangement of the ommatidia 
being normal. When animals with eyes of these two kinds are mated 
together what is lacking in one is compensated by its presence in the 
other, and the offspring ought to be quite normal in appearance, since 
the three defects, lack of coloured pigment, lack of white pigment, and 
imperfect form are all recessives. 
The theoretical analysis is as follows for the case of the albino carrying 
black and red crossed with a red no-white :— 
If W represents the factor for the presence of white pigment and w 
that for its absence, the other letters being used as before :— 
WWecBRxwwCCRR 
Albino carrying Black and Red Red no-white 
Male Gametes We BandWcR 
Female Gametes w CR 
KF, Zygotes W. ww, CocsBaks WwCcRR 
Black with the white normal but Red with the white normal 
carrying red, albino and no-white. carrying albino and no-white. 
