262 Action of the Genetic Material 



phenocopies produced after shock treatment as the result of quanti- 

 tative interference with rate processes in development and their inter- 

 locking actions, whatever the primary eflFects, identical or not identical, 

 for mutants and phenocopies may have been. This idea, first worked 

 out in explanation of the above-mentioned experiments with butter- 

 flies before the phenomenon of phenocopy was properly established 

 (Goldschmidt, 1918, 1920a), and since presented repeatedly (e.g., 

 1935a,Zj, 1938fl, 1940), covers the overwhelming majority of facts. An 

 immense, partly experimental material is available, also, from the 

 study of teratogenesis. Ancel (1950) has recently assembled a good 

 deal of it in a book, and, though he has never heard of the extensive 

 amount of work on phenocopy, is forced to draw conclusions almost 

 identical with mine. 



These discussions and my earlier ones (Goldschmidt, 1938a, 

 1940) should make it clear why I have considered and still consider 

 the phenomenon of phenocopy the basic phenomenon for any study 

 of genie action. Landauer (1952Z?), who recently contributed so much 

 to our subject, expresses the same attitude by referring for comparison 

 to the results of radiation work. He quotes Pontecorvo saying that we 

 would not expect to get a deep insight into the nature of a ship by 

 studying the efficiency of di£Ferent types of gunfire in sinking it. "The 

 same skepticism should be applied to the hope that studies on the 

 developmental effects of major mutant genes will lead to an under- 

 standing of the role in growth and development of those genes which 

 make up the normal genotype of fowl or any other higher organisni 

 . . . Studies on the production of phenocopies, together with the 

 search for means by which the organism can be protected against 

 such experimental modification, may offer a technique with which 

 the holes made by our experimental gunfire may be repaired . . ." 



C. CHEMICAL PHENOCOPIES 



In the discussion of Landauer's work, we have anticipated one 

 aspect of the work on chemical phenocopies, because we wanted to 

 show that, in principle, chemically induced phenocopies will find the 

 same explanation as all others, though the causation of that part of the 

 effect which is identical in mutant and phenocopy may involve com- 

 pletely different primary actions. Even in Landauer's experiments the 

 different agents employed had a certain specificity of action upon 

 beak, extremities, and skeleton, though al) of them acted in a similar 

 way. The most interesting facts on such specificity of action have been 

 found in Drosophila. 



