LOSS OF EYE-PIGMENT IN GAMMARUS. 287 
SECTION II. THE ALL-WHITE PERFECT EYE. 
In the former paper (p. 45 and Fig. 8) a second form of white eye, Le. 
one of perfect form but with no black or red retinal pigment, and with 
only the extra-retinal chalk-like white accessory pigment, was described 
and figured. This occurred in the pure red stock and the details of the 
origin of the only two indviduals of the kind that were seen are given 
in the paper referred to. Only one individual, a male, survived to pro- 
duce offspring. The stock has not since produced any more of them. 
Cross C. 
CROSS BETWEEN ALBINO IMPERFECT-EYED FEMALE ACB ANDES So ArT 
WHITE” PERFECT-EYED MALE R.]1. (Plate VIJ, Figs. 4 and 7: 
Plate IT.) 
The male just referred to was mated with an albino imperfect-eyed 
female (AB) from the degenerate-eyed stock described on p. 275. There re- 
sulted 2 black and 3 red-eved offspring all normal eyed as regards form, 
and the male died in moulting without mating again (Plate IT). The fact 
that two parents, neither of which showed any coloured pigment, produced 
all coloured-eyed offspring seemed to make this case specially interest- 
ing and some pains have been taken to investigate it thoroughly. Since 
the male came from pure red stock, and some black-eyed offspring were 
obtained it seems clear that the black came from the female which must, 
since both black and red offspring were produced, have contained the 
red factor also. This female was therefore an albino carrying both black 
and red, like the sister from the same brood whose offspring we have 
already studied in Cross A. 
There seem to be two possible ways of regarding this case, in which 
two albino parents produced coloured offspring. Following Bateson 
and Punnett we may endeavour to explain it by supposing that the 
factor for red has been lost in the perfect-eyed male, whilst a “ colour 
factor,” which must be present if colour is to appear, has been retained 
in the male, but is absent in the female. If we represent the colour factor 
e that 
of the female On the other hand, it may be that the absence of 
by C and its absence by c, the constitution of the male would be 
colour in the male is a somatic and not a germinal character, and is not 
inherited at all. Breeding experiments carried on to the fourth genera- 
tion have shown that this second supposition is the true one, and that 
the “all-white ” male from the pure red stock behaves. as regards its 
offspring, exactly as if it were a pure red. 
