No. 575] 



AN APTEROUS DROSOP1I1LA 



cm 



which has been long known, and often mentioned, 10 but 

 by no means universally recognized. 



Correlated with, or resulting from this principle is the 

 conception that the final result of ontogenetic develop- 

 ment is not due to the independent action of various 

 factors and their products, but is due to the combined 

 action, or the interaction of these products during devel- 

 opment. To illustrate by the wing of a fly, — it is probable 

 that the normal development of such an organ is not 

 dependent solely upon one factor, but that it is influenced 

 by many factors. This is strongly suggested by data 

 derived from the various wing mutations in Drosophila. 

 These have dealt with a large number of factors, each of 

 which is responsible for a definite wing modification. For 

 instance, one factor is responsible for miniature wings, 

 another for vestigial, another for rudimentary, another 

 for curved, etc. 1 1 From the fact that these mutant factors 

 (which may be considered as modifications of factors in 

 the normal fly) influence the wings, it seems highly prob- 

 able that their normal allelomorphs also influence wing 

 production in the wild fly. 



Finally I wish to thank Dr. T. H. Morgan for kindly 

 assistance and advice in connection with this work. 



BIBLIOGRAPHY 



Dexter, John S. 



1912. On Coupling of Certain Sex-linked Characters in Drosophila. 

 Biol. Bull, Vol. 23, p. 18.3. 

 Morgan, T. H. 



1911. An Attempt to Analyze the Constitution of the Chromosomes on 



