No. 60S] MULTIPLE FACTORS IX MICK AM) HATS 403 



wild mice descended from a few indivKluals caiituicd at 

 Forest Hills, and at Wenham, ;Mass. Tlu' !■', m'licraiion 

 obtained by crossing the "blaze" and (liluti" brown self 

 races is all self lu character. The I\ jj;eneration shows 

 a distribution of yoinii? recorded in line 2, Table III. 



It will be seen that the extr('nu'> cf vai'ialulitv in 1\ are 

 the same as in the pure inl)r(Ml wild lilazc race. F., F,„ 

 and Fr, animals raised witlionf srhcimi/ uixc a result 

 recorded in line 3 of Table Jl. and auam ^liow the same 

 limits of variation. It will be seen, tlioreforc, that the 

 blaze character is segreg-ated from the cross without 

 apparent modification, although the extremely minute 

 degrees of spotting which it includes are those which one 

 might expect would be modified or entii'eh -wainped if 

 contamination between the uaiuetc- ot the mmI and l>laze 

 races occurred. This cross to-rt hci' with iiie cro-- be- 

 tween mutant and wild rats recoided bx ( a-tle to be con- 

 sidered later, give conclusive e\ idenee that even a minute 

 quantitative character segiea.it* - alt* i < io--inu and does 

 not afford liTounds for the obieetion raided bv Castle that 

 cio^M- ]n\^MHm laM- dittemiu d^iitK m ^i/e or like 

 fliietuatin- .■harartei- do not readilv -how M-re-ation. 



To -iiMi up 111. i.-ii !- or-|..tiinu iili.iituK. m mue. 

 it ma> Ix' -aid tli.it all tlu < lo-, - n a h -Imu .i n ipp. ir- 

 ance of grand] uaivntal condition- m I-V,. back cro--. and 

 other advanced hvbnd u-en.'i-a t lon^. '1 li.' reaj^itcai'anee 



one to conclude that if segre<>-ation m a -tnctlv Mendelian 

 sense is not taking place, tliat at lea-t the out w ard apptear- 

 ances of such a process are all of tlieni pt e-ent. 



