THE ANALYSIS OF A CASE OF CONTINUOUS 

 VARIATION IN DROSOPHILA BY A STUDY 

 OF ITS LINKAGE RELATIONS 



PROFESSOR JOHN S. DEXTER, 

 Olivet College 



I. Introduction. 

 II. The Germinal Constitution of Beaded Flies. 



B. Crosses between Beaded Flies and Other Mutants. 



1. The F, Generation. 



2. Linkage Relations. 



(a) Sex Linkage. 



(b) Linkage to Sex-linked Genes. 



(c) Linkage to Second Chromosome Genes. 



(d) Linkage to Third Chromosome Genes. 



III. The Effect of Environmental Conditions on the Development of Beaded 



Wings. 



B. The Effects of Relative Moisture. 



C. The Effects of Covering with Parafiine the Mouth of the Bottle 



in which the Flies are Developing. 



D. The Effects of Acidity and Alkalinity. 



E. The Effect of Relative Temperature. 



F. The Effect of Darkness. 



IV. The Effect of Selection on the Production of Different Types of Bead- 



B. Perfect Notched Wings. 



D. Stumpy Wings. 

 VI. Summary. 



Hardly had the principles of Mendelism been worked 

 out in one species of plant than apparent exceptions to 

 these principles were discovered. Mendel's own case of 

 the breeding true of species hybrids in Hieracium was the 

 first of these, and since 1900 others have been reported. 

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