146 ''Latency^' [ch. 



in all its characters hypostatic — or recessive, to use the 

 simpler if less accurate term — to all the factors of the albino, 

 the composition of the albino may be seen even from F^. 

 For instance, when bred to a pure black, a GG albino will 

 give greys only ; a GB albino will give equal numbers of 

 greys and blacks ; while a BB albino will give blacks only. 

 Conversely it is possible to manufacture by suitable matings 

 albinos of each composition. For example, albinos extracted 

 from chocolates can only bear the chocolate determiner. 

 Those from black mice must all bear the black determiner 

 if the families have been large and no chocolate has occurred. 

 So, those from greys must all bear the determiner G, li in 

 sufficient numbers no blacks or chocolates have been pro- 

 duced. With regard to pattern and saturation or dilution 

 of colour the case is exactly the same. An albino from 

 Dutch-marked parents cannot bear the self-colour factor, 

 and one from blues cannot bear the saturation-factor. 



It is this fact, that in most cases the albino will be 

 bearing the determiner proper to the colour of the last 

 coloured parent from which it was extracted, which has led 

 several writers to speak of these colours or patterns as 

 " latent " in the albino. This mode of expression is much 

 to be regretted. There is no ''latency" of black, or grey, 

 or self-colour, as a whole in the albino. Certain factors 

 which are essential to the production of those features may 

 be present in any albino of unknown origin, but this fact 

 does not in any way touch the question of the purity of the 

 germ-cells, as has been quite erroneously suggested. Sul- 

 phate of copper is blue and chloride of copper is green, but 

 it would be incorrect to speak of blue as latent in sulphuric 

 acid, or of green as latent in hydrochloric acid ; nor has the 

 acid obtained from chloride of copper more of "greenness" 

 in it than has the same acid obtained from sodium chloride. 



Taking the evidence respecting the genetics of colour as 

 a whole, though much remains which is obscure, as has 

 been stated, especially in the discussion of yellow in the 

 Rodents, there can be no reasonable doubt that with rare 

 exceptions it will be found possible to express the whole 

 series of phenomena as due to the combination and re-com- 

 bination of a limited number of recognizable factors which 

 are treated by the cell-divisions of gametogenesis as units. 



