-! 
LOSS OF EYE-PIGMENT IN GAMMARUS. a 
Red carrying Albino by B+ A and A+B: 141 Black, 44 Albino. 
Red carrying Albino by B+R+A and A+B+R,; 217 Black, 177 Red, 
182 Albino. 
To sum up, 60 red-eyed animals were tested, 49 gave definite results, 
36 proving to be Red with the albino factor, and 13 Pure Red. Theory 
demands 36:6 Red with albino, 12-2 Pure Red. 
These results are in full agreement with Hypothesis IT and not in agree- 
ment with Hypothesis I. 
Cross C. F.2, GENERATION. ALBINOS. 
A final test of the two hypotheses would be obtained by testing the 
I; albinos got by crossing F, coloured parents. Amongst these F, albinos 
: : Spee NUN) Se nc ‘ 
animals with the constitution ~ like the original all-white male parent 
C 
should occur if Hypothesis I were true. If therefore we make many 
crosses amongst the albinos of this generation we ought to find some 
pairs which would give all coloured offspring. If these are not produced 
it will be an additional proof that Hypothesis II is the right one. We 
have made 18 matings of this character, and they yielded a total of 588 
young, all of them albino.* 
* In all the animals referred to in this paper as ‘‘albino,” the eyes had the irregular, 
degenerate form figured on Plate VII, Fig. 4. If we take the view that, in the absence of 
red and black pigment, the regular form is in itself sufficient to distinguish the ‘‘ all 
white ” eye (Plate VII, Fig. 7) from the imperfectly shaped ‘‘albino’’ eye, the following 
statement, the form of which we owe to Prof. R. C. Punnett, who has been good enough to 
read this paper in proof, puts the argument against our Hypothesis I in a brief form. 
The letter P must be understood to represent the factor for either red or black pigment, 
p the absence of such a factor. Hypothesis I. That two complementary colour factors are 
concerned, of which the ‘‘albino ” female contains one, viz, P, and the ‘‘all white” male 
the other, viz. C. 
All white g x Albino ¢ Albino 9 x Black 2 
CCpph (x ceRP. CCR Pade CORP 
Females Males 
VAG LB VL. Ca'Cekp CoRR eAy Tibi: 
(Plate IT) Se ——— (Plate IT) 
Site 2) 
= Cp \ es (CP & 
Soc in) a \cP & 
® ep — R 
CCPP 
Ce PP 
CCPp 
Ce Pp Zygotes of broods 
Cc PP VARI VISAGE ViloAG 3), 
ce PP Vi Bali Vals 2. sVilsBas., 
Ce Pp WARC HIE, sVA ORs a Vile Crd 
ce Pp (Plate IT). 
Mated among themselves the chances of Pp zygotes coming together are 16 in 64, i.e. 
1 in 4, and in such cases ‘‘all-white” eyes should appear in ratio 1:3. Amongst the 
blacks 109 such matings have been made, amongst the reds 40, and amongst the albinos 
27, making a total of 176 such matings, and no “all-white” eyes of perfect form appeared. 
Hence Hypothesis I is not valid here. 
