THE GENE 



317 



in the classic researches of Dorfmeister, 

 Standfuss, Merrifield, Weismann; or for 

 the behavior of seasonal-dimorphic butter- 

 flies, as has been discussed in detail by 

 the present writer ('17, '2.0b, '2.3c, 'z7a) 

 and controlled experimentally by his 

 former student Siiffert ('14); or further for 

 the many instances of phenotypic identity 

 of modifications and mutations. For our 

 present discussion, however, the impor- 

 tant point is the demonstration that 

 definite genes are really connected with 

 definite rates of reaction. 



There have since appeared other investi- 

 gations which in our opinion lead to the 

 same result. We mention first Zeleny's 

 (^3) work on the influence of temperature 

 upon the bar eye in Drosophzla. This 

 author concludes from his experiments: 

 "Perhaps the most interesting point in 

 connection with the present data is the 

 demonstration that they furnish of the 

 fact that the gene ultrabar has the same 

 type of reaction as a temperature difference. 

 It is possible to state the effectiveness of 

 particular germinal factors in terms of the 

 corresponding effects of temperature." 

 And further: "In view of the fact that 

 temperature is effective only during a 

 few hours of larval life, it may be con- 

 sidered that the initial steps in the forma- 

 tion of ommatidia are confined to a 

 definite embryological period. (This 

 applies also to the butterfly wing. R. G.) 

 The length of this period is determined by 

 the general physiological processes of the 

 larva, while the rate of formation of 

 ommatidia during the period is a function 

 of special processes, which have a different 

 coefficient." The present writer thinks 

 that with the introduction of the concep- 

 tion of velocities of reaction into Zeleny's 

 results they fall completely into line with 

 his conclusions. In addition we recall 

 that it has been shown for the bar-genes 

 with which Zeleny worked that it is 

 their quantity which counts. 



A very remarkable piece of work which 

 leads in the same direction has been done 

 by Plunkett ('2.6). He studied the effects 

 of temperature upon bristles in Drosophila, 

 trying to exclude all disturbing factors. 

 The results — mainly a consistent reduction 

 of bristle number with increasing tempera- 

 ture — were minutely analyzed. Some of 

 his conclusions are: The essential differ- 

 ence between the dichaete and wild-type 

 flies (so far as bristles are concerned) is 

 the velocity of a bristle-reducing reaction. 

 The effect of this continuous reaction, 

 namely bristle or no bristle, takes place 

 if the concentration of the produced sub- 

 stance equals or exceeds a certain threshold 

 value. The action of the gene, then, is 

 the production of a chain of reactions, 

 namely: the gene produces from a proto- 

 plasmic component, the distribution of 

 which means localization, a catalyst JR, 

 the concentration of which is typical for 

 the respective gene. For this production 

 of K the gene itself may be the catalyst. 

 The concentration of K is again propor- 

 tional to the velocity of a reaction, the 

 already mentioned reaction for the produc- 

 tion of bristles, conceived as decomposi- 

 tion of a thermolabile bristle-forming 

 catalyst B. Here then we have again 

 all the elements of the present writer's 

 old conception of the action of the gene by 

 definite velocities of reactions, producing 

 the formative substances. But there is 

 one difference: not the quantity of the gene 

 but the quantity (concentration) of a 

 product of the gene, the catalyst K, is 

 linked with the different velocities. We 

 have seen already that ample proof is 

 existant to show that the quantity of the 

 gene itself is decisive, whatever the 

 intermediate points of the chain or 

 reactions might be. Thus Plunkett's 

 work, as far as it goes, confirms the 

 present writer's former conclusions. It 

 might be added that Plunkett draws 

 general conclusions from his analysis 



