v] TRANSFORMATIONS 43 



(Chironomus) as described by Miall and Hammond 

 (1900) the brain is situated in the thorax, and the 

 imaginal discs for the head, eyes, and feelers of the 

 adult lie in close association with it, though they arise 

 from inpushings of the larval head. These rudiments 

 do not appear until the last larval stage has been 

 reached. In the gnats Culex and Corethra, on the 



Fig. 11. Front region of Maggot of Blow-fly (Calliphord) 

 showing diagrammatically the imaginal discs, which are 

 shaded, e, eye; /, 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 Kees, Zool. Jahrb. 

 1894, and Lowne's Blow-fly. 



other hand, the imaginal discs for the head-ap- 

 pendages retain their normal position within the 

 larval head, and appear in an early stage of larval 



