that it might be indirect evidence of sex hormones and Wiggles\A'orth (1954) 

 felt that hypertrophy might be an indication of storage. It is unhkely that the 

 ovaries of Calliphora have any direct influence on the с a., for when ovariecto- 

 mised females are fed sugar without protein the с a. do not hypertrophy but 

 remain small. When castrated females are fed protein in addition to carbohydrate 

 their c. a. increase in size in relation to the amount of protein ingested, and 

 when protein is removed from the diet the с a. decrease in size. The induced 

 c. a. volume cycles are the same in normal and ovariectomised females provided 

 the same quantity of protein has been ingested, but this is true only up to the 

 stage at which yolk is deposited. At this stage, if an additional quantity 

 of protein is ingested the с a. volumes of normal flies increase slightly more 

 but decrease during yolk deposition. The с a. of castrated females, on the 

 other hand, increase to about twice the volume of those in yolk depositing 

 females, and then these also decrease but do so more gradually. In normal 

 females, с a. volumes decrease during yolk deposition, but the decrease can be 

 eliminated by forcing the flies to ingest excess protein during this phase. 



It is suggested that the assimilation of protein leads to an accumulation 

 of activating substances in the blood and that these quantitatively stimulate 

 the c. a. either directly or via the m. n. c. Utilisation of the substances by the 

 tissues and particularly by the ovaries during yolk deposition decreases the 

 concentration in the blood which in turn leads to a decrease in с a. activity. 

 This theory fits the facts fairly well, for protein is ingested in large quantities 

 during the pre-yolk phase луЫ1е the с a. increases in volume, but as the assimi- 

 lated materials are deposited as yolk and as protein ingestion decreases, so the 

 volume of the с a. becomes smaller. 



It is further suggested that с a. volume fluctuations represent activity 

 fluctuations, for the findings described above and later can not, it is felt, 

 be interpreted in terms of storage-release cycles. 



Activation of the с a. does not appear to be by nervous pathways. The dener- 

 vated с a. of flies retaining their ovaries and of ovariectomised females remain 

 small when sugar alone is ingested. If protein is also consumed, the denervated 

 o. a. become larger in reproducing females and hypertrophied in ovariectomised 

 flies. If the cardiac-recurrent nerve or the nervi oesophagei are cut, the с a. 

 are smaU in sugar flies but increase in volume when protein is ingested. 



Protein, its breakdown products, its precursors or some other substance 

 present in the protein-containing mixture appears to be necessary for с a. 

 activation. The fact that equal amounts of j^rotein rapidly dissapear from the 

 ahmentary canals of both normal and ovariectomised females, yet result 

 in the c. a. of ovariectomised females becoming hypertrophied suggests that 

 activation is humoral rather than an influence from the gut. 



What controls protein ingestion and digestion? 

 Removal of the m. n. с results in females ingesting practically no protein, 



138 



