THE HIDDEN TYPE OF WING-GROWTH 135 



or excretory tubes, each of which a very short distance from 

 its origin divides into two, so that the maggot has four of these 

 tubes, the same number as the fly. 



The nervous system of the maggot shows a most remarkable 



Hf- > h 



int 



FIG. ?8 DIAGRAM OF THE NERVOUS AND DIGESTIVE SYSTEM 

 OF A MUSCOID MAGGOT. 



br, brain : s.g., ventral ganglion with diverging nerves ; 

 ph, pharynx ; oe, gullet ; c, crop ; s.gl, salivary glands ; 

 pc, pyloric caeca ; s, stomach; kt, kidney tubes ; int, intestine ; 

 r, rectum. Position of imaginal groups of cells shown by black 

 patches, x 10. Adapted in part from Lowne and Hewitt. 



concentration. The brain (Fig. 78 br), consisting of a pair of 

 compound ganglia, lies above the gullet some distance back from 

 the mouth in the thoracic region of the larva. Immediately 



