1. A study has been made of the effects of removal of ovaries, copora allata (c.a.) and median neurosecretory cells (m.n.c.) upon the selection by female blowflies of carbohydrate (sugar in water) or ‘protein’ (Marmite in milk).
2. Extirpation of the ovaries resulted in high carbohydrate-low protein selection and in hypertrophy of the c.a.
3. Extirpation of the c.a. resulted in low carbohydrate selection.
4. Extirpation of both ovaries and c.a. resulted in low carbohydrate selection.
5. These and other results suggest that selection is independent of direct ovarian control, but that the ovaries influence selection in that they utilize the ingested foods and thus bring about the succession of feeding cycles.
6. The c.a., whose volume (activity?) changes cyclically during each cycle of reproduction, appears to control the fluctuations in carbohydrate consumption.
7. The m.n.c. seem to be necessary for the ingestion of ‘protein’ and for the activity of the c.a.
8. Reproductive cycles tend to overlap. The succeeding cycle in a gravid female must be taken into consideration when events are being related to reproduction.