392 Action of the Genetic Material 



be so limited that the quantity of each pigment can increase only at 

 the expense of the others (which then is a threshold phenomenon), 

 depending upon the relati\e dosage of the respective mutants. Antho- 

 cyanin may be cyanin or pelargonidin. In Dahlia the factors A and B 

 do not control one or the other; the alternative is rather decided by 

 the entire quantitative system of the factors involved. Thus, synthesis 

 of pelargonin, a derivative of pelargonidin, requires the following: 

 (1) presence of AiBiY; (2) t\vo or more B; (3) one or more B with 

 three I; (4) one or more B with two or more I and at least one A; 

 (5) one or more B together with one I and at least three A. 



This whole scheme of genie collaboration is visualized by making 

 the arbitrary assumption that the limit of the source of pigment avail- 

 able in Dahlia under whatever genie combinations can be stated to be 

 six units. Now B and Y are capable of using the maximum source in 

 simplex condition, and thus contribute at least six potential units. A 

 has a cumulative potential value which in quadriplex condition is less 

 than or equal to the maximal source. Thus unit values are calculated 

 for Y = 9, B = 6, I = 1, A = /2, and their combined action would be, 

 if 8 is the threshold value for pelargonidin, A4I4 = 6 units, or B1A2I1 = 

 8 units (i.e., only cyanin). AiYi = 9.5 and Bo = 12 units (i.e., only 

 pela'-gonin ) . Hence it is concluded that each factor competes for the 

 common source in terms of its potential units, and the total pigment 

 depends upon the proportion and power of interaction of all factors. 

 Also, a chemical interpretation is proposed, namely, that the actions 

 in terms of units are involved in controlling the oxidation of the 

 phenyl ring. 



So much for Lawrence and Scott-Moncrieff. For our present dis- 

 cussion of the orderly interplay of genie actions it is not important 

 whether every single point of this analysis is unassailable or has actu- 

 ally been corrected since. The important point is that in a concrete 

 case in which much knowledge is available the interplay of genie 

 reactions points to some of the same physicochemical processes which 

 are met always: velocities of reaction, quantities of reaction products, 

 dosage efiFects upon both, threshold conditions caused in diflFerent 

 ways, nature of the substrate, and competition for the substrate, in 

 addition to the production of the specific enzymes and the precursor 

 substrates of different complexity. Though it is very difficult to visu- 

 alize such an interplay at the proper places in the four dimensions of 

 embr>'onic determination under genie control, it helps at least toward 

 forming a vague image, which is the maximum available today, while 



