LOSS OF EYE-PIGMENT IN GAMMARUS, oot 
tion in both eyes, and in their offspring the no-white strain appeared. (Out 
of 76 young produced by this pair 38 were Red-eyed, 29 with normal eyes, 
3 with one eye normal and the other no-white, and 6 no-white on both sides ; 
38 Albinos, 22 of which were normal-eyed and 16 no-white, i.e. Colourless. 
Two of these young albinos have mated, and had 41 young, 33 normal 
Albino-eyed and 8 Colourless, which is the usual 3:1 ratio. The Colourless 
have also had offspring, 8 all Colourless.) 
In Brood 5, one Red-eyed had the right eye practically no-white, with only 
a fleck or two of white pigment, left eye normal. (Examined again at maturity 
the right eye was found to have developed the normal white reticulation, 
cf. p. 340.4.) One Albino had the left eye Colourless. (In the first brood of 
13 young of the next generation one Red-eyed had the left eye no-white, 
and very little white pigment in the right eye.) 
In Brood 6, one Red-eyed animal had the right eye no-white, and one 
Albino had the left eye Colourless. (In the next generation one Red had the 
left eye no-white, and very little white pigment in the right eye.) 
In Broods 7 and 8, which were not examined for some days after extrusion, 
the animals were all normal-eyed. 
In Brood 9 three Red-eyed animals were affected, one with the right eye, 
one with the left eye, and one with both eyes no-white ; and two Albinos, 
one having the right eye and one both eyes no-white. 
In Brood 10, all the animals were normal-eyed. 
In Brood 11, one Albino had the left eye no-white. 
In Brood 12, two Reds had both eyes practically no-white. 
In Brood 13, one Red had both eyes practically no-white. 
In Brood 14, three Red-eyed were affected, two had the right eye and one 
had both eyes no-white. 
A number of other Reds in Broods 10 to 14 showed a tendency for the 
white reticulation to break down. 
In Brood 15 two Red-eyed had the right eye no-white, and one of the two 
had the reticulation much broken on the left side. Two others had the re- 
ticulation so much broken, one on the right and one on the left, as to be 
practically no-white, and in many others the reticulation was very thin. 
One Albino had the right eve affected, there being only one spot of the white 
pigment at the upper end of the eye. 
In Brood 16, two of the Red-eyed had the left eye practically no-white. 
In Brood 17, three Red-eyed were affected, one with the right eye, and 
two with the left practically no-white. 
In Brood 18, one Red-eyed had the nght eye no-white, and one Albino 
had the right eye no-white, and a very small eye on the left side. 
In Brood 19, one Red-eyed was no-white on both sides. 
In Brood 20, all the animals were normal-eyed. 
In Brood 21, one Red-eyed had the right eye and one had the left eve no- 
white. 
In Brood 22, two Red-eyed had hardly any white pigment in the eyes, and 
one Albino had the left eye Colourless. 
NEW SERIES.—VOL. XI. NO. 3. DECEMBER, 1917, Z 
