SOMATIC MUTATIONS OF BRUCHUS. 21 



characteristics, like material substances, are chiefly derived from 

 the mother." The facts upon which are based the conclusions 

 recently drawn from a study in asymmetry in Peromyscus by 

 Sumner and Huestis ('21) are not necessarily contradictory to 

 Conklin's point of view, in spite of their statement that "the 

 chromosome mechanism of heredity ... is ill-adapted to account 

 for the transmission of definite spatial relationships. . . ." Future 

 evidence bearing upon the question of symmetry will be very 

 welcome. 



SUMMARY AND CONCLUSIONS. 



1. During the years 1918 to 1920, among the thousands of 

 Bruchid insects examined, thirty-one elytral mosaic females were 

 found in homozygous cultures of the black, white, and tan stocks. 

 The usual expectancy from pure cultures is that the elytra of the 

 normal female will be red-red for the red mutant, black-black for 

 the black one, white-white for the white mutant, and tan-tan for 

 the wild type, but such mosaic types as red-black, black-red, black- 

 white, black-tan, tan-black, and white-tan have appeared from 

 homozygous cultures. These display the same order of dominance 

 as was discovered by the author ('21) for the four body colors 

 (red, black, white, and tan or the wild type). 



2. Chromosome elimination of any kind is not essential to ac- 

 count for these mosaics, but a dominant somatic mutation in one 

 chromosome of the pair is the most plausible explanation. The 

 time in the ontogeny at which the mutation occurred would govern 

 the extent of its effects; the earlier that it took place, the greater 

 its effect. It is evident that it did occur at the time when the 

 anlagcn of the wings were differentiated, otherwise an elytral 

 mosaic would not have appeared. 



3. The difference between the factor mutations which the author 

 ('21) discovered for the body and elytral color factors located at 

 the locus R (red), in an autosome and its somatic mutations as 

 manifested in these elytral mosaics, is that the former are trans- 

 mitted, while the latter are not. There appears to be a somatic 

 continuity, however, between this gene for R (red) in this auto- 

 some in the germ cell and this same gene as manifested through 

 its thirty-one somatic mutations. 



