No. 608] MULTIPLE FACTOBS 7.V MICK AX I) RATS 461 



the first row of Table II that, in this race, animals 

 varying from 56 to 96 per cent, were obtained. There is 

 a tendency for a mode to be formed between 80 and 92 

 per cent. The Japanese race used is one which for sev- 

 eral years has been closely inbred and which holds remark- 

 ably true to type. Its range of variation is shown in the 

 second row of Table II. It will be seen that the animals 

 possess from 4 to 36 per cent, of the dorsal surface pig- 

 mented. A distinct mode is observed between 13 and 16 

 per cent. 



race with the -ell' dihitt In own oi lunwn .i-^uti aniiiinl- 

 above referred to, con^-t- of -ohd ^oloied aiimiaK and 

 is therefore not to be recorded. The {generation in 

 wliich 14() piel)ald animals have been recorded con- 

 tains mice ranging from 20 to 96 per cent, pigmented. 

 Among the 146 animals recorded, 20 or 13.6 per cent, fall 

 in grades characteristic of the Japanese grandparents. 

 94 or 63.6 per cent, are of grades found in spotted animals 

 of the other grandparental race, see Table II, line 3. 

 Two other generations of great interest have been tabu- 

 lated. The first of these, line 4, Table IT, i^ the result of 

 back crossing F, generation animals with animals of the 

 Japanese parent race. In this o-i'iiei-iition tlici-e is di-tinct 

 evidence of sc<;T(><>-atioii. F'lftv five of the 1.11 niiiiiials 

 recorded fall within the limit- of the .fapam-v -land- 



