148 THE INTERNAL STRUCTURE OF THE FULL-GROWN LARVA 



containing these three pairs of major cephalic discs, which will 

 form the cephalic capsule. 



In addition to these two other pairs of cephalic discs are 

 found. A pair of small flask-shaped maxillary rudiments are 

 situated one at the base of each of the oral lobes ; a second pair 

 of imaginal discs, similar in shape to the maxillary discs, is found 

 adjacent to the hj^postomal sclerite ; the latter, I believe, are the 

 labial rudiments, and will form almost the whole of the proboscis 

 of the fly. 



The tJioracic discs. 



In 21. domestica there are five pairs of thoracic discs. The 

 prothoracic imaginal discs (figs. 53 and 66, pr.d.) are attached to 



Fig. 66. Transverse section of mature larva anterior to the ganglion and cerebral 

 lobes to show the position of certain of the imaginal discs. The body-wall 

 and muscles have been omitted. The folded character of the adipose tissue 

 laminae can be seen in this section, and also the degenerating anterior portions 

 of the malpighian tubules {in.t.). (Camera lucida drawing.) 



an.d. Antennal disc. c.r. Problematical cellular structure (Weismann's "ring"). 

 c.v. Caecum of ventriculus. (/.jh.s. Dorsal mesothoracic (alar) imaginal disc. 

 f.c. Adipose tissue cell. l.tr. Lateral tracheal trunk. m.t. Malpighian 



tubule cut rather longitudinally. oe. Oesophagus. jir.d. Prothoracic 



imaginal disc. v.ms. Ventral mesothoracic imaginal disc. 



