352 Eye-Colour in Gammarfis 



in all the survivors to a thin thread-like reticulation. This reduction 

 of the white pigment took place gradually. All those examined when 

 half-grown were found with very thin reticulation, whilst at maturity 

 some eyes could not be distinguished from typical No- whites, in others 

 only a fleck or two of white was left ; in others one eye had developed 

 into No-white, and one had thin reticulation ; in some again the " spots " 

 had disappeared. There was not one single instance in four generations 

 of an animal reaching maturity with the reticulation normal. 



The details summarised are as follows : — 



In the ^1 generation ; 22 young, 10 of them spotted, 1 No-white in 

 Right eye : H survivors, all practically No-white. 



In the F2 generation, spotted matings ; 88 young normal-eyed, 34 of 

 them spotted: 11 survivors, 2 one-sided No- whites, the others either 

 practically or completely No-white. 



In the Fs generation, unspotted matings; 34 young normal-eyed, 

 7 of them spotted : 9 survivors, all became completely No- white. 



In the F3 generation, spotted matings ; 32 young normal-eyed, 

 18 spotted : 4 survivors, 1 completely No-white, the others practically so. 



In the Fi generation, unspotted matings ; 56 young, 1 of them No- 

 white in Left eye, 1 with very heavy white reticulation in Left eye, the 

 others normal-eyed, 40 of them spotted: 7 survivors, No-white and 

 practically No-white. 



The F2 and F.^ generations were crossed, spotted matings ; 47 young 

 of which 41 were spotted, and 4 with rather heavy reticulation : 4 sur- 

 vivors — No- white. 



The F2 generation from these crosses, spotted matings ; 38 young, 

 28 of them spotted, 2 with heavy reticulation. 



IV. Spots. 



In the Albino-eyed stocks used in the experiments the white extra- 

 retinal pigment shows a tendency to break up, and portions of it become 

 detached from the eye. These form definite spots of chalk-white pigment, 

 and these spots do not contain ommatidia (Plate XIV, Fig. 6). What 

 appear to be exactly similar white spots have occurred from time to 

 time in all the experimental stocks (red, black and hybrid), but they 

 seem to run in particular families. They are especially frequent in the 

 Albino stock, and to a less extent in Red carrying Albino. The spots 

 vary greatly in size and shape, being most often small spherical masses, 

 at other times becoming white streaks of varied length and width, and 



