EFFECTS OF DUCTLESS GLANDS ON FLIES 



259 



TABLE 2 



Showing the effect on the length of larvae of feeding thyroid exclusively . The first 

 line indicates the distribution of the thyroid-fed larvae according to length, the 

 second line indicates the distribution of the controls which were fed on muscle 



Thyroid 



Muscle 



Length in mm. 



1 



5 

 12.5-12.9 



In order to compare the effects of thyroid and thjrmus feeding 

 on the length of the larvae, reference may be made to egg mass 

 No. 20. This was a very large egg mass numbering nearly 200. 

 Portions of the eggs were placed on'thyroid and thymus of a calf, 

 respectively. At the end of four days the larvae were killed with 

 boiling water and measured. The average length of 107 thyroid 

 larvae was 11 mm. and that of 71 thymus larvae was 14 mm. 

 (tables). 



TABLE 3 



Showing the effect on the length of larvae of feeding thyroid and thymus, respectively. The 

 first line indicates the distribution of the thyroid-fed larvae according to length, the second 

 line indicates that of the thymus-fed larvae 



Thyroid... 

 Thymus... 

 Length in 







2 



17-17.9 



The effect of thyi-oid feeding on the duration of larval life could 

 not be determined with great accuracy, as pupation is retarded 

 if the larvae are prevented from burying themselves or if they are 

 disturbed after burial. The length of time during which the 

 larvae feed is not affected markedly by the ductless glands 

 selected for the experiment. This is rather interesting in view of 

 the fact that the pupation of mature larvae of Lucilia caesar may 

 be retarded in several ways; such as by cutting off the supply of 

 oxygen, as Dewitz ('01) has shown. I have noticed also in my 

 own experiments that if the substratum is too dry the pupation 

 of mature larvae may be delayed from forty-eight hours, which 

 is normal, to four or five days. 



Nearly all my evidence indicates that there is some hastening 

 of maturity effected by feeding thyroid gland to larvae of the 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 26,N0.2 



