E. J. Allen and E. W. Sexton 361 



from Experiment IX, had 332 unspotted young and 41 spotted (i.e. ll°/o 

 spotted). Two of their young ^3, also both spotted dorsally, had one 

 brood of 12, 8 of which were spotted. 



In another Experiment, an F^ male mated with two females, all 

 dorsally spotted, had with the first female 170 unspotted and 17 spotted, 

 i.e. 9 7o» ^iid with the other 41 unspotted and 11 spotted. 



Summary. In the Coloured Spotted strain experimented on, when 

 unspotted animals were mated together, families were obtained in which 

 the percentage of spotted young varies from °l^ up to 18 °/^. When 

 spotted animals were mated a similar result was obtained and the per- 

 centage of spotted was not increased. 



If the percentages of spotted for the different families in these and 

 other experiments of a similar kind are arranged in order (taking only 

 those families composed of 50 or more individuals) they form a fairly 

 continuous series from to 18 °/^ of spotted. 



The eye-colour of the parents, i.e. whether the eyes are Black or Red 

 or Hybrid Black (black carrying red) makes no difference in the per- 

 centage of spotted offspring. 



B. Experiments to establish a Pure Spotted Strain. 



The Albinos always give a much larger proportion of spotted than 

 the Coloured Stocks ^ so it was decided to try to establish a Pure 

 Spotted Strain amongst them. For this purpose a family (C. 176)^ was 

 taken, which had given a very high percentage of spotted through several 

 generations (cf. p. 358). 



As the Albinos carry either Pure Black or Pure Red or both Black 

 and Red which do not show unless mated with Coloured, and as we did 



1 When Albinos are mated with Coloured carrying Albino, the Albino offspring always 

 give a much higher percentage of spotted than do the Coloured offspring, as the following 

 instances show : 



1. Albino X Colour carrying Albino, neither spotted : Fi young, 44 unspotted and 

 2 spotted Coloured ; 28 unspotted and 9 spotted Albino : percentage of spotted Coloured 

 4-3 %. of spotted Albino 24-3 %. 



2. Albino x Colour carrying Albino, neither spotted : Fi young, 76 unspotted and 

 1 spotted Coloured ; 56 unspotted and 13 spotted Albino : percentage of spotted Coloured 

 l-3°/o, of spotted Albino 18-8%. 



3. Albino x Colour carrying Albino, one spotted : Fi young, 85 unspotted and 14 spotted 

 Coloured ; 41 unspotted and 29 spotted Albino : percentage of spotted Coloured 14'17o, 

 of spotted Albino 41-4 °l^ . 



2 This family was descended from a pair of spotted Albinos, the male being VI. C. 2 r 

 and the female I. G. 1 c, shown on Plates I and II, Allen and Sexton, 1917. 



