THE MUTATED GENE 251 



6. The basic pattern itself is affected by a shift of the relative 

 distance (or size) of the elements. Example: enlargement or 

 restriction of the field of symmetry in the flour moth (Kuehn and 

 Henke, 1929-1936). A dominant mutation is involved here. 



7. The basic pattern is affected by suppression of some of its 

 elements. Example: the recessive mutant lunata of L. dispar, 

 (Goldschmidt, 1927c, 19336) showing no zigzag bands in the 

 system of symmetry. 



8. The whole basic pattern is changed into a quite different 

 pattern. (Examples: mimetic Papilios, De Meijere, Fryer, 

 Poulton, and collaborators; see Ford, 1936), where the process is 

 sex controlled and dependent upon a few recessive genes and their 

 recombination. 



These are the types of genetic facts, which are to be correlated 

 with the embryological facts in order to gain a general insight 

 into the all-important problem of the production of pattern by the 

 action of genes. It may be added that a large bulk of similar 

 genetic evidence could be cited regarding the control of pattern 

 by mutant genes in the caterpillars of Bombyx and Lymantria 

 (Toyama, 1906a; Tanaka 1913, 1916; Goldschmidt, 19216, 

 19286) ; in the larvae and imagos of chrysomelid beetles (Tower, 

 1906; Tenenbaum et al., 1933). But in all these cases, the addi- 

 tional experimental and embryological knowledge are missing. 



There is little difficulty in explaining all these cases in which 

 genes control differences within the pattern (change from red to 

 yellow, melanism overlaying pattern). The action of the 

 mutant gene is of the same type as has been described. It does 

 not involve the problem of pattern itself. Goldschmidt (1927c) 

 worked out a theory designed to reduce this problem to the 

 already known principles regarding action of the genes. His 

 interpretation may be stated in general terms thus: The genes 

 controlling pattern act by producing definite, reactions of definite 

 velocity. These are properly timed; i.e., their time elements 

 are arranged so that the thresholds of effect are reached in a 

 definite order, thus insuring for each process a definite situation 

 upon which to act. In the known cases where there is genie 

 control of the velocity of differentiation in different areas of the 

 pattern, at a given moment two such areas are found in a different 

 stage of development. If, now, another gene-controlled reaction 

 leads to the production of, say, guanin, to be deposited in the 



