360 ROSCOE R. HYDE 



PRODUCTIVITY OF THE EXTRACTED TRUNCATES 



If it be true that the fertility of the extracted truncates is more 

 than twice as great as the original truncates and if it be true 

 that the egg production of the extracted truncates is increased, it 

 follows that if the extracted truncates be bred together in pairs 

 their productivity should be greatly increased. To judge from 

 the previous history of the truncates in regard to productivity 

 (Part II ; table 1) and the attendant low fertility we should expect 

 that by doubling the fertility of the gametes of the truncates that 

 they would produce between 100 and 125 offspring on an average 

 to the fertile pair instead of 50 as formerly. The number of off- 

 spring produced above 125 would, in a rough way, give a measure 

 of the increased egg production. This does not take into con- 

 sideration, any difference that may exist in the length of life 

 between the truncates and extracted truncates. It would seem 

 from the tables that the extracted truncates had been benefited 

 to some slight degree in respect to the length of life as a result of 

 extracting from a wild stock. 



In order to throw some light on the question just raised, I bred 

 together a number of these extracted truncates in pairs. These 

 flies were from the same source as those used in the previous experi- 

 ments. The pairs were made up August 9 and 10 and discon- 

 tinued on September 1 . The final count was made September 1 1 ; 

 consequently the total number of children produced is not repre- 

 sented. The results are given in tables 4a and 4b. Ten pairs of 

 truncates were used to control this experiment but it was evident 

 from inspection that their productivity was practically the same 

 as in former experiments and consequently the offspring were not 

 counted. A study of the table makes it certain that it is possible 

 not only to put fertility into the truncate stock but also increased 

 egg production. Consequently the productivity of the truncates 

 has been raised from 50 to about 300 as a result of crossing, out 

 and extracting. Since the fertility of the extracted truncates is 

 twice as great and the productivity six times as great it follows 

 that egg -production has been increased three fold — from 200 to 



