/l/ utilization Judged by effect of the element on fecundity. /2/ Utilisation Judged by Influence of the element on occurrence of 

 alate forma. /5/ Reported by acme (q.v.) as not utilized by Drosophlla except possibly In trace aaiounta. /U/ In balanced solu- 

 tion only. /5/ Universal constituent of protoplasm. /6/ Absent from chemically defined nutrient medium except as hydrochlorides 

 of amlno-acldfl or vitamins. /?/ Toxic for this organism. /8/ Based on non -utilization of cobalamln. /9/ As PbCNO,)p. /lO/ Re- 

 placeable by magnesium, /ll/ Utilized as KOH but not as KCl. /12/ Absent from the chemically defined nutrient medium except as 

 occurring In sulfur containing amino acids. 



21 



