[Illustration: Fig. 11. Front region of Maggot of Blow-fly (_Calliphora_) showing diagrammatically the imaginal discs, which are shaded. _e_, eye; _f_, feeler; _W_, fore-wing; _w_, hind-wing; 1, 2, 3, legs. _H_ is the "cephalic vesicle," which becomes everted at the close of the metamorphosis, so as to bring the feelers and eyes to the front, the brain (_B_) moving forwards at the same time. After Van Rees, _Zool. Jahrb._ 1894, and Lowne"s _Blow-fly_.]