SOMATIC MUTATIONS OF BRUCHUS. 13 



appeared in any pure culture of red. This fact is significant be- 

 cause red is dominant to black, white, and tan, and if recessive 

 mosaics through mutations occurred in the red stock, they could 

 not be seen. It is of interest to observe that all thirty-one elytral 

 mosaics were females; the reason is, the colors (red, black, and 

 white) are somatically visible in the elytra of this sex, but, on the 

 other hand, no elytral mosaic males were discovered because the 

 elytra of the males of the four types are always tan. Therefore, 

 if a mosaic was produced in a male, it could not be seen, because 

 the characters involved are sex-limited traits. 



Twenty-two of these mosaics, described in Table I., originated 

 from homozygous, black cultures. Each of these mosaic females 

 was alike in having a normal black body, except that one elytrum 

 was always red. Of these, eight (Mosaics 5, 12, 13, 17, 21, 25, 26, 

 and 28) had a red, left elytrum and a black, right one, while four- 

 teen (Mosaics i, 2, 4, 7, 8, 9, 10, n, 15, 19, 22, 23, 24, and 27) 

 had a black, left elytrum and a red, right one. In order to deter- 

 mine whether a factor mutation had occurred, each of these mosaic 

 insects was mated to a homozygous, black male, and the number 

 of offspring from each pair is given in Table II. The result is the 

 same from every mating; red was not transmitted because all 

 progeny were pure for black. No doubt the fact that red is the 

 only dominant to black explains why the red elytrum was visible. 

 The fact that the black mutant cultures are more prolific and, 

 accordingly, give rise to a greater number of offspring might ac- 

 count for the appearance of more mosaics, unless it is assumed that 

 the mutation from black to red occurs more frequently. 



In order to illustrate the red-black, elytral, mosaic type, let us 

 describe Mosaic 12 (Tables I. and II.) as an example. This in- 

 sect appeared on December 12, 1918, from a pure, black culture. 

 She had a red, left elytrum and a black, right one. She was mated 

 to a pure, black male, because her body color was, likewise, 

 homozygous for black; her progeny were every one pure for the 

 black character. Among the 1,712 offspring no red ones were dis- 

 covered ; however, red was visible in the mother because it is a 

 dominant color to black, which is its recessive allelomorph. 



From the fourteen black-red, elytral mosaics let us select Mosaic 

 9. This animal emerged from a culture which was homozygous 



