JOSEPH KRAFKA, JR. 449 



The Sex Coefficient at Different Temperatures. 



A marked sexual difference exists in all these experiments. The 

 average value for the ratio between the mean facet number of the 

 females and that of the males is 0.791. Temperature has no consis- 

 tent effect in altering this ratio. 



An explanation of the sexual difference is to be sought in the fact 

 that we are dealing with a sex-linked factor. On the chromosome 

 hypothesis, a double dose of the restricting factor is present in the 

 female while only a single dose is present in the male. 



Inheritance of Temperature Effects. 



Comparison of Offspring Raised at 27°, from Parents Reared at 15, 20 y 



and 27° , Respectively. 



The interest in this phase of the work is both practical and theoreti- 

 cal. To preclude any inherited effect in the stock experiments, care 

 was taken to keep the parent stocks at 27°. To determine whether 

 or not there was an inherited effect. Experiment 51 was designed. 

 Flies reared for one generation in the stock experiments at 15, 20, and 

 27° were used as parents in cultures that were made up under condi- 

 tions as nearly alike as possible. The offspring from the 15° parents, 

 from the 20° parents, and from the 27° parents were thus allowed to 

 develop simultaneously at 27°. 



The distribution of the facet counts of the parents and the off- 

 spring is given in Table XXIII. The mean facet values and the stan- 

 dard deviations are given in Table XXIV. The mean facet number, 

 the standard deviation, and the distribution of the F: stock reared at 

 27° are characteristic of the 27° stock counts although those of the 

 parents are markedly different. There is no inherited effect of tem- 

 perature upon facet number in this case. 



