EFFECTS OF DUCTLESS GLANDS ON FLIES 



261 



thyroid culture there were 46 pupae and 29 larvae. That is, less 

 than 9 per cent of the muscle larvae had pupated in the time in 

 which over 60 per cent of the thyroid-fed had pupated. Eleven 

 days after deposition there were 54 pupae in the muscle culture 

 and 66 in the thyroid. 



The experiments to determine the effects of thyroid feeding on 

 the size of the pupae were on the whole rather disconcerting, 

 for although accurate measurements were possible there were less 

 constant and definite differences from the controls than in the 

 experiments with the larvae. In two experiments with L. 

 sericata the pupae derived from muscle-fed larvae were markedly 

 longer than those derived from thyi'oid-fed. A similar difference 

 was noted also in one of the experiments with L. caesar. In 

 two experiments to compare the effects of thyroid and thymus 

 feeding, there was a very slight superiority in the length of the 

 thyroid-fed pupae. In two experiments, on the other hand, in 

 which egg masses were placed on muscle and thymus, respectively, 

 there was a superiority in length among the thymus-fed. It is 

 evident that the results are not striking and that the effect of 

 thymus and thyroid probably are to a slight extent in accord with 

 the findings of others who have worked with tadpoles. 



Egg mass No. 13 of L. sericata is typical of a number of experi- 

 ments. Larvae were fed exclusively on calf thyroid and muscle. 

 After ten days all the larvae in both cultures had pupated. The 

 distribution of the pupae is indicated in the following table 

 (table 4): 



TABLE 4 



Showing the effect on the length of pupae of Lucilia sericata of feeding the larvae 

 exclusively on thyroid. The first line indicates the distribution of the thyroid-fed 

 pupae according to length, the second line that of the muscle-fed 



The average length of the thyroid pupae was .295 inch; that 

 of the muscle pupae was .296. This difference, of course, is too 

 small to be significant. 



