INHERITANCE OF EYE-COLOUR IN GAMMARUS. 25 
215 young were counted, all black-eyed ; some of these have commenced 
breeding. 
This generation is very interesting from the fact that in it, as in the 
same generation of the original stock, a deviation from the normal 
occurred. In the case of the original stock the black pigment was absent, 
and the result was a red eye with the superficial network of opaque white 
pigment unaltered. In this second case the black pigment was present 
in every instance, but in the broods of Pair V the white pigment was 
affected in greater or less degree. The female of this pair had less white 
than is usual in the eye—the reticulation was perfect, but the lines of 
white were very thin and thread-like. The eyes of the young in the first 
generation were the same, but in the young from the first pair of these 
that mated there was considerable variation. One brood of 13 contained 
2 young with “‘ no-white” eyes on both sides (Fig. 6), 5 others with 
the white reticulation very faintly marked, and 6 with eyes like the male 
parent and female grandparent. This brood is being kept separate 
to see if the defect follows the Mendelian lines of inheritance of 
characters. 
No individuals of the third generation from these pairs have been 
hatched yet (Nov. 19, 1915), but 60 which have been examined from 
the General Stock bowl all have normal black eyes. 
The summer dredging was taken on July 6, 1915. 372 hving animals 
were examined, all black-eyed. A good many more were brought in, but 
did not survive overnight, owing to the heat and overcrowding of the pots 
and consequent fouling of the water. 
Twenty-two adults were mated with Red mates; 31 broods were 
counted, containing 348 young, all black-eyed. 
Thirteen black-eyed pairs of those paired in the ditches were separated 
from the others, and placed in finger-bowls to breed to the second genera- 
tion. By November 19, 1915, there were 127 of the first generation and 
one brood, 5 in number, of the second generation, all with black eyes and 
all normal except the offspring of one pair. In this bowl, four of the first 
generation were left, two females with normal eyes, and two from a 
younger brood, one with normal eyes, and the other with a white patch 
on each eye at the upper end caused by three or four of the ommatidia 
being unpigmented, the “ part-white ” eye (cf. Fig. 7 for an example of 
this in the Recessives). This is the first occurrence recorded in the course 
of the work of a variation appearing in the first generation from animals 
brought in from the ditches.* 
* Only one specimen has been recorded from freshly captured animals, a male, with 
the left eye affected. 
