THROWING BACK i^ 



on tlie following page, did the exact ratio occur. 

 The total numbers obtained in my experiment were : 

 Group A, 137 ; Group B, 287 ; Group C, 134. 



Now let us consider the breeding properties of 

 the mice representative of the three groups, A, B, and 

 C. The albinos (Group A) breed true without excep- 

 tion. With rare exceptions, the mice in Group B 

 again produce representatives of Groups A (No. 15), 

 B (Nos. 16 and 17), and C (Nos. 18 and 19), when 

 they are mated together ; the exceptions referred to 

 do not produce albinos or fawns, but only mice with 

 black eyes and dark coats — that is to say, they breed 

 true to the characters of Group B. The mice in 

 Group C, with very rare exceptions indeed, breed 

 true to the characters of their group. 



The breeding properties of the various colour 

 types within the three Groups, A, B, C, are as follows, 

 so far as my published records permit me to judge : 

 Black by black do not give grey ; but grey by grey 

 may give black, as also may grey by black. Lilac 

 by lilac do not give fawn ; but fawn by fawn have 

 not yet given lilac, nor have lilac by fawn. Self- 

 colour by self-colour occasionally give piebalds, but 

 piebald by piebald do not give " selfs," and piebald 

 by " selfs " give both piebalds and " selfs." It is 

 desirable now to pause and to consider the pheno- 

 menon represented on Plate II. as a whole. 



The parallel between this phenomenon and that 

 exhibited by, for instance, tallness and dwarfness 

 in the pea, or by the colour of the Andalusian fowl, 

 is at once obvious. Albinism may be called the 



