252 



Sturtevant. 



Table XI. 



same cell? Is there anything corresponding to interference taking place 

 between different chromosomes? Morgan and Lykch ('12) have pub- 

 lished data showing that linkage may occur in chromosomes I and II at 

 the same time, that in the first being of the expected strength. But 

 crossing over in 11 could not be detected, because it was obscured by 

 no crossing over in the male. The case is, then, of no value for our 

 present purpose. I have carried out two small experiments along this 

 line, and they are recorded in table XXIII. The result involving chromo- 

 somes I and III may be graphically represented thus: 



MW PEb 

 187 



MW P JEb 



101 



MtW PEb 

 8 



änw p jEb 







The experiment is obviously inconclusive, since so few cross-overs 

 occurred between P and Eb that their distribution with regard to the 

 other cross-over is not significant. Tlie cross does, however, show that 

 two groups may show their usual linkage in the same individual — a 

 point which is of interest in connection with the views of those who 

 look upon linkage as a "reduplication" phenomenon. The other cross, 

 involving chromosomes I and II, is summarized below: 



The numbers are too small for the index of interference (1'43) to 

 be significant; but the result shows that crossing over may occur in 

 two chromosomes at the same time. 



