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INHERITANCE OF EYE-COLOUR IN GAMMARUS. 45 
Another instance is that of Exp. 99 (p. 38), a Pure Black male from 
Bf, mated with a Recessive female, both with normal eyes. All their 
young, 86 in number, were also normal. In the F, generation the “ no- 
white ” and the “ part-white ” strains appeared in the offspring of a pair 
from Brood 7. This pair had three broods, the first brood of 6 died young. 
Of the second brood, 21 in all, 13 Black and 8 Red, only 7 survived, 3 
Black males, one with the left eye affected (in this case 2 or 3 of the omma- 
tidia formed a little cluster apart from the ommateum). 4 Red survived, 
two normal and two “ part-white ”’ as figured (Fig. 7). (In the first brood 
from these Reds 3 out of the 4 young (F,) had normal eyes, the fourth 
had eyes like the male figured.) The third brood numbered 30, 20 Black 
and 10 Red, of these 6 survived, 4 Black and 2 Red, only one normal-eyed 
amongst them, a Black. Two of the other Blacks were “no-white” on 
both sides, and the remaining one was normal on the right side, but had a 
small cluster of ommatidia apart on the left side. Of the two Reds, one 
was ‘‘no-white ” on the left side, the other had the white reticulation 
partly lacking, i.e. partly “ no-white.” 
Many cases have occurred in which the white pigment (instead of being 
diminished or lacking) is present in excess. This appears to be always 
accompanied by a diminution of the coloured pigment of the retinular 
cells, the red, e.g., being hardly perceptible, even with a strong lens 
showing only as a very pale pink tint, instead of the vivid blood-red of 
the normal red eye. This variation has been noticed especially in the 
later generations of the inbred Recessives, and it is possible that another 
generation or two of inbreeding may produce the “ all-white” eye. 
Only a few “ all-whites”” have been recorded so far (Nov. 19, 1915). 
Two, a male hatched April 2, 1915, and a female hatched April 14, have 
appeared in the Pure Red Stock amongst the young from Brood 4, Exp. 5, 
Recessives (p. 27) (descendants of the fourth brood of female A of the 
original experiments, p. 22). The female came to maturity but died 
without mating. The male (Fig. 8) was mated with female B (Figs. 9 and 
10), referred to below (a Hybrid with degenerate “white” eyes), and 
proved pure Red—the 5 young being normal-eyed, 2 Black and 3 Red. 
It died in moulting, November 19, 1915, without mating again. ‘Two 
other females from the same brood as the “ all-white” female extruded 
their young in the brood-bowl, 6 in number, all with very pale pink, 
almost ‘‘ white ” eyes. 
A curious instance of -the ‘‘ all-white” accompanied by degeneration 
of the eye was noted in the forty-second brood of M family, F, Hybrids 
(p. 31). This brood was extruded on June 1, 1915, and numbered 12 
young, 7 Black, 1 Red, and 4 “ all-white ” eyes. These four proved to be 
1 male and 3 females. The male mated with one of the females, eggs were 
