56 



Scientific Proceedings (103). 



Conclusions. 



The results of the various experiments are obvious from the 

 records. It need merely be pointed out that in none of the dupli- 

 cates were we able to repeat the gas figures exactly and that for 

 quantitative measurement the test needs further standardization 

 to be efficient in comparing solutions. The great variability of 

 the yeast loopfuls obtained in this method would easily give rise 

 to considerable variation and experiments are being made along 

 this line to be reported later. 



As a means of studying presence of "B" Vitamine in large or 

 small quantity and as an index more reliable than rat feeding 

 experiments the test offers such marked advantages in sensitive- 

 ness and in speed of observation that it seems well worth while to 

 devote more time to its improvement. 



32 (1492) 



Two sex-linked lethals of simultaneous appearance in Drosophila 



obscura. 



By D. E. Lancefield (by invitation). 



[From the Zoological Laboratory, Columbia University, New York 



City.] 



A pair mating in Drosophila obscura (Fallen) produced a sex 

 ratio of 106 females to 22 males. This was about a 1:4 ratio and 

 indicated a case of two sex-linked lethals, or lethals at two loci 

 on the X-chromosome. Both lethals (li and I3) appeared simul- 

 taneously in the same culture from a female whose mother did 

 not carry a sex-linked lethal, as was shown by the normal sex 

 ratio produced by her; and the father could not have carried such 

 a lethal and lived. 



Three daughters inherited both lethals in the same chromosome 

 with a sex-linked gene producing the character "short" wing veins. 

 These three females produced a total of 352 females to 40 normal 

 and 50 "short" males. Such a count suggested that the gene 

 for "short" was between the two lethals, which were far enough 

 away from it for each to segregate almost independently from it, 



