LINKAGE OF THE FACTOR FOR BIFID WING. 163 



SUMMARY. 



The strength of linkage between the factor for bifid wing 

 and the factor for vermilion eye is approximately the same 

 (viz. 32 units) in the original cross in its reciprocal, and in the 

 F 2 from the crossovers of the original. (See Experiments I., II. 

 and III., Tables II., III., V. and VI.) 



The strength of linkage between yellow body color and bifid 

 wing is constant (viz. 5 units) in the original and in the 2 from 

 the crossovers (See Experiment IV., Tables VII., VIII. and IX.). 



A repetition of Experiment IV. showed a linkage value (viz. 

 6 units) not significantly different from that previously found. 

 The linkage moreover is constant in the two reciprocal crosses 

 of this experiment. (See Experiment V 7 .; Tables X. and XI.) 



The strength of linkage between white eyes and bifid wings is 

 preserved in the crossovers (viz. original 8, crossover 9 units), 

 but is different in the reciprocal (viz., 4). (See Experiments VI. 

 and VII.; Tables XII., XIII. and XIV). 



A modification of experiments VI. and VII. gave a strength of 

 linkage (viz. 5 and 6), which approaches that of the reciprocal 

 (viz., 4) but not the original linkage value (viz., 8). (See Experi- 

 ments VIII. and IX.; Tables XVI. and XVIII.) 



In all of the experiments of this paper the strength of linkage 

 is apparently not changed by a previous crossing over between 

 the factors in question. 



The linkage value given by the females is the same as that 

 given by the males of the same experiment. (See Tables XVI. 

 and XVIII.) 



Crossovers appear in the F 2 generation equally frequently 

 among the first flies hatched as among those hatched last. 

 That the factor for yellow body color has an effect on the via- 

 bility of flies is evidenced from the deficient numbers of yellow 

 flies in Tables VIII., X. and XI. A deficiency also occurs in 

 flies with white eyes as compared with those possessing red eyes. 

 (See Tables XIII., XVI. and XVIII.) A bifid wing factor, how- 

 ever, does not seem to have any such effect ; the bifid winged flies 

 comparing favorably with the long winged flies (see Table 

 XVIII.). 



UNIVERSITY OF CINCINNATI, 

 May 6, 1914. 



