INHERITANCE OF EYE-COLOUR IN GAMMARUS. 49 
7. The Pure Dominants and the Recessives breed true through all 
generations. 
8. The crosses which have been made and the young hatched from them 
are as follows :— 
Pure Black x Recessive.—3779 black-eyed young ; 3746 in paper, 33 in 
control experiments. 
Hybrid Black x Recessive.—4255 young, of which 2176 were black-eyed 
and 2079 red-eyed. Those referred to in the paper numbered 4189, 
2138 Black and 2051 Red, the others came from other experiments 
in the F, generation—-not included. 
Pure Black x Pure Black.—All black-eyed young, 1715 in number. 
Pure Black x Hybrid Black.—All black-eyed young, 379 in number. 
Hybrid Black « Hybrid Black.—4393 young, of which 3327 were black- 
eyed and 1066 red-eyed. Those referred to in the paper numbered 
4302, 3259 Black and 1043 Red—the other 91, being from the F, 
experiments, not included here. 
9. The absence or diminution of the white pigment seems peculiar to 
some broods. The “ no-white”’ eye appeared in the second generation of 
offspring of Pure Black animals brought in from the ditches. The indi- 
viduals affected in this way are more difficult to rear than the others, and, 
so far, attempts to breed them have not been successful. 
10. The absence of the coloured pigment and degeneration of the eye 
occurred also in the F, generation—in this case from Hybrid Black 
animals. 
11. The absence of the coloured pigment in perfectly formed eyes, the 
“ all-white” eye, occurred in the Recessives. A great diminution of the 
red pigment has also been observed, particularly in the F, generation of 
the inbred Recessives. 
12. The absence of the coloured pigment in part of the eye, the “ par¢- 
white” eye, was observed in the first generation of offspring of Pure 
Blacks brought in from the ditches. It has been noted several times in 
both black and red eyes of specimens bred in the Laboratory, but only 
once in fresh-captured material. This case was a male, with one eye 
affected. 
13. About as many males as females survive to maturity. 
14. The breeding together of animals from different generations gives 
the same results as regards proportions of colours as the breeding together 
in the same generation. 
NEW SERIES.—VOL. XI. NO. 1. MARCH, 1916. D 
