128 s. IKEXO : 



ftoui white-II X orange, and since we see there the complete Hnkage between 

 the factoi-s H and U, it would not he probable tliat it ha5 had that composi- 

 tion fi-om the very beginning ; in all probabiUty it has been at fii'st of the 

 constitution CCBBBB, changed into CCRBBb hy a "loss-mutation", 

 and then undergone the segiegation alxjye stated. 



In all cases imder I above enumerated (and in some cases iinder III) I 

 haye assumed that the reversion takes place dming the formation of gametes, 

 l,ut it would le equally possible that this process of mutation occm'S, not 

 dming the gametic formation, Imt some time before in the somatic cell. To 

 cite one instance for illustrative pm^pose, in No. 6 (Table YIII) where 

 white-I (ccrrbh) giyes rise to orange of the constitution Cct'rhh the 

 process m&j I'e as follows : — a somatic cell of the constitution cci'rbb gets 

 that of Ccrrbh by revei-sion ; such cell produces dming each succeeding 

 cell-division the cells Ccrrbb, so that in the reducing division the gametes 

 of the constitution Crb and crh are formed. (Compare the discussion 

 in p. 124 . If what is above described be true the whole process of revereion 

 in I (and also in some cases imder III) is essentially identical with that in 

 II. To determine exactly in each individual case which alteruatiye will be 

 realised, i.e. whether the reyei-sion occm'S in the somatic cell or fii-st in the 

 formation of gametes \\'ould be an almost impossible task in the present state 

 of om' knowledge. 



rV. Each of the F, magenta parents in Nos. IC, 17 and IS, derived 

 from the cross wliite-II x magenta has segi'egated x\i\m magentas and whites, 

 and produced in addition 1 orange, 1 flesh-coloured and 1 pseudo-white. As 

 tliis segiegation has given rise to 90 magentas and 42 wliites in total, i. e. 

 99 ±4-97 and 33±4'97 respectiyely on 3:1 expectation we may in all 

 probability regard each magenta pai-ent in our case to be of the constitution 

 CcBBBB- The question, howeyer, to what kind of mutation will 1 e due 

 the production of flesh-colom'ed and pseudo-white plant in this case would be 

 quite imexplainable, especially as the exact genotyi^ic «imixisitiou of the two 

 latter is j-et unknown. 



In respect to Nos. 19 and 20 we may consider that the i^ magenta 

 imi-ent is homozygous, i.e. of the constitution CCBBBB and has bi-ed hiie 



