334 Action of the Genetic Material 



checking upon phcnotypic effects of difFerent genie conditions and, 

 where possible, also to take into account observable features of the 

 timing in develoj)ment. Thus such studies directly continue our former 

 discussion of the genie control of steps of determination. This former 

 discussion related to the material system which permits the genie 

 material to control the orderly sequence in time, and the pattern in 

 space, of embryonic diversification, a system involving the interplay 

 between nuclear genie material and cytoplasmic substratiun. Now we 

 shall attack the same problem by studjing the over-all effects of di- 

 verse genie setups in regard to their quantitative aspects. This is all 

 that is meant by kinetics in the present discussion. 



We first introduced the kinetic point of view of genie action 

 when, in our experiments on intersexuality, a relation between the 

 time of incidence of a developmental feature (the turning point) and 

 an assumed quantitative feature (quantity or potency of sex deter- 

 miners) was found ( Goldschmidt, 1917a, 1918), relations which could 

 be best explained in terms of reaction velocities. Sewall Wright (1916) 

 presented similar ideas at the same time. But we must keep in mind 

 that we are trying to explain morphological features and that, there- 

 fore, the kinetics of genie action will, in the end, result in some 

 properties of substances and structures. Therefore, I cannot agree with 

 Hersh's (1941) distinction of substance-minded and relation-minded 

 thinking, which I prefer to consider as belonging together as two 

 facets of the same thing. Hersh expresses his views thus: "The sub- 

 stance-minded type of thinking . . , has all the tenacity of original 

 sin. In morphology it has given us representative particles, preforma- 

 tion, the transmission of acquired characters, and such morpho- 

 chemical hybrids as bristle-producing, facet-fonning substances, and 

 so on. The morphologist when substance-minded, thinks of the devel- 

 opmental patterns in terms of the visible structural characteristics from 

 stage to stage. In short, he thinks in terms of a series of pictures. But 

 when relation-minded, the morphologist recognizes that the pattern 

 at any moment is the expression of the events which produce it, and 

 attempts to gain a knowledge of the durations and rates, and relative 

 durations and relative rates, of the component processes in the de- 

 velopmental nexus. Consequently, instead of thinking in terms of a 

 series of pictures, the relation-minded morphologist tends to think in 

 terms of the non-picturable. If the problem of the developmental pat- 

 tern is similar to the problems of the more exact sciences, then no 

 doubt in time a system of equations will be developed to facilitate our 

 thinking about it." 



