LOSS OF EYE-PIGMENT IN GAMMARUS. 325 
39 red-eyed young in three broods. The experiment was not carried 
further. 
The “ Part-white”’ Eye. 
The “ Part-white ’ animals referred to in the former paper, p. 43 
(Hig. 7), were also investigated, as it appeared probable that the 
abnormality might be related to that of the “ All-white ” perfect 
eye. 
In the “ part-whites,” the eye was of perfect form, the chalk-white 
accessory pigment was always present, and most of the ommatidia were 
normal, with black or red retinal pigment developed; some of the 
ommatidia, however, were quite colourless, thus giving the effect of a 
patch of white on the eye. 
The brood in which the ‘“ part-whites ” first appeared consisted of 
21 young, 13 black and 8 red. Of the red, 4 survived to maturity, 2 being 
part-white, male and female. The left eye of this male was figured 
(Fig. 7 in former paper), in the right eye two or three ommatidia were 
colourless, and on the inner side two ommatidia were separated from 
the ommateum, one pigmented and one unpigmented. The other 
~ part-white,” a female, had a cluster of 9 colourless ommatidia in the 
right eye and 5 in the left. These two mated several times, but no egos 
were laid, and the female died. The male was then mated with a normal 
red-eyed female and had 30 young, all normal red-eyed animals. These 
died before reaching maturity. 
The male was then mated with a Pure Black female, also a part- 
white, with a large patch of white on the upper side of the ommateum of the 
left side, and a small patch in the same position on the right side. This 
female came from wild stock brought in on July 14, 1915, and left to 
breed till February 11, 1916. When examined on that date, 60 young 
were found, 59 normal black-eyed, and the ‘ part-white ” female just 
mentioned, . 
The result of the mating was a brood of 22 young, all black-eyed. 
They were left to mate together and on October 3, 1916, 44 young were 
found, 22 black and 22 red, all normal-eyed. 
These young were left to mate together and on February 22nd, 1917, 
the pots were examined. There were then present 73 young, 36 black 
and 37 red, all normal-eyed. 
It seems certain therefore that the “ part-white ” character is not 
inherited. 
