1921.] Research in Animal Breeding. 259 



A long series of expeiiments has shown us that 3 pattern — 

 types corresponding to Dutch, spotted Dutch, and White Dutch 

 can be got to breed approximately true. Ihe more piguiented 

 tends to be dominant to the less pigmented, but as a rule 

 dominance is far from complete, so that vai-ious intermediate 

 forms arise. Two pairs of factors T-t and S-s serve to inteipret 

 the range of forms between Dutch and White Dutch, Dutch being 

 TTSS, Spotted Dutch ttSS; and White Dutch ttss. 



The relation of all these to the more heavily pigmented grades 

 is determined by another factor P ; its presen: e represents much 

 increased pigmentation. A single dose of P added to Wliite 

 Dutch transforms the animal into one with a pattern resembling 

 the Dutch* ; added to Spotted Dutch, it leads to a grade of pig- 

 mentation between Dutch and self-colour; added to Dutch, it 

 results in an animal that is almost or quite self-coloured. Where 

 the animal is PP the White area is further diminished, but the 

 difference between PP and Pjj animals has not yet been fully 

 worked out. 



The outstanding fact in connection with these patterns is 

 that analysis of this continuous series, from self to almost 

 white, has provided an interpretation in terms of the factorial 

 theory; and that, too, in terms of but 3 factors. 



♦ The Ppttss animal may be in(listinp;-uishal)le from th^ppTTSS animal in 



api)earance, l)iit the two hrecl vci v (litTcii'Uilv. 



E 2 



