THE AMEBIC AN NATURALIST [Vol. XL VIII 



adult flies that had been etherized several times (usually 

 twice a day) just after they had hatched: 



Black vestigial (8 times) 694 



Pure black (6 times) 81 



Finally some of the flies that had appeared, in the ex- 

 periments in which 8 and 10 drops of ether had been used 

 throughout the larval and pupal life, were bred and gave 

 in the next generation the following records : 



In a grand total of 31,168 flies subjected to ether, there 

 was not a single mutation observed. It seems highly 

 probable therefore that ether has no specific effect in pro- 

 ducing mutations in Drosopliila ampelophihi. It might, 

 of course, still be said that mutations are so rare, that, 

 although caused by ether, they still are not frequently 

 enough produced to make 31,000 flies a sufficient guaran- 

 tee. Granting this, it still remains that since no mutants 

 appeared under this excessive treatment, ether does not 

 play the role of a specific agent causing the. mutations of 

 Drosopliila, and one is inclined to look elsewhere for a 

 solution of the problem. 



One of the first mutants that I observed in ampclophila 

 appeared in the offspring of flies that had been treated 

 with radium and although there was no proof that the 

 radium had had a specific effect I felt obliged to state the 

 actual case, refraining carefully from any statement of 



