No. 530] XOTES AND LITERATURE 



511 



heredity are due to changes in the relative amounts of suhstanees 

 produced by the metabolic activities within the cell. 



Even white varieties, which are frequently referred to as 

 having lost the factor for color, may originate merely from a 

 change in the quantity of some substance or substances present. 

 That many white flowers do not owe their lack of pigment to the 

 absence of a pigment-producing factor is shown by the fact that 

 such flowers frequently show pigment in exceptional individual-, 

 and many white flowers develop more or less pigment with age. 

 Pre>uinab]y, as the flower passes its prime, there may be changes 

 in the rate at which various metabolic processes go forward, and 

 this may induce pigment formation. 



In Science for May 31, 1911, Professor Morgan gives some 

 interesting data concerning the origin of a number of mutations 

 in Drosophila. In a culture treated with radium one fly was 

 produced the marginal vein of whose wings was headed, and this 

 character appeared in a very small proportion of the next 

 generation. The proportion of headed wings increased from 

 generation to generation until a stock was produced that gives, 

 in certain cultures, nearly 100 per cent, of the new character. 



In the seventh generation of the beaded- wing stock a fly ap- 

 peared with the end of the wings cut off nearly squarely, and 

 indented at the ends, or somewhat scalloped. This character is 

 confined almost exclusively to the female line. In the next gen- 

 eration twenty-one flies, with truncated wings, appeared along 

 with 230 having normal wings. In the third generation some of 

 the truncated-winged flies produced nearly 50 per cent, of 

 truncated wings. 



In the second generation of the headed-wing flies a male ap- 

 peared with wings shorter than the abdomen. A similar muta- 

 tion occurred in a related stock. These abnormal flies bred 

 together have produced 964 normal males and females, six short- 

 winged males and two females. 



In the seventh generation of the beaded-wing stock a fly 

 appeared with wings like the normal in form but extending no 

 further than the end of the abdomen. This character proves to 

 be sex limited. 



Occasionally flies have appeared, especially in the truncated- 

 wing stock, with each wing swollen up to a balloon or a bladder 

 filled with fluid. Practically a pure stock of this mutation is 

 now on hand. 



Several times flies have appeared that failed to develop black 

 pigment in the body. These flies have produced no offspring. 



