ANATOMY OF THE GOUT-FLY OF BARLEY. 



795 



delicate ventral commissures which do not unite the trunks them- 

 selves but corresponding branches. No other ventral commissures 

 could be discovered. The second tracheal trunk on each side 

 gives ott' a backvvardly-directed branch; these two branches con- 

 verge to the dorsal surface of the brain, where they are joined by 

 a short trnnsvere commissure. From here they continue back- 

 wards, one on each side of the dorsal lobes, and pass downwards 

 one on each side of the (Esophagus, probably ending in the ventral 

 tracheal plexus. 



Text-fio;ure 10. 



0-5 mm. 



Dorsal commissures and tlieir tracheal brandies in A. Chlorojp.i tceniopus, 

 13. Balioptera combinata, and C. Merotnyza nigriveniris. 



All the lateral trnnks except the first two bear a small 

 appendage (v.t.) appearing as a very short tracheal branch. An 

 attempt to investigate tlie nature of these by means of sections- 

 Avas not completely successful, but indicated that they were 

 solid strands directed towards the lateral body-wall and in all 

 probability attached to the latter. They are probably vestigial 

 stigmatic trunks such as have been recorded by Imms (8) in the 

 larva of Anopheles, and by Carpenter and Pollard (2) in the larva 

 oi IIy])oderma. 



Perisiigmatic Qlands. 

 Lying at the base of each posterior stigmatic papilla just ventral 

 to the tracheal trunk and close to the hypoderm, is a gioup of two 

 or three somewhat flask -shaped cells. A duct leaves each cell, and 

 the three ducts join forn)ing a common duct which passes back- 

 wards towards the stigmatic plate, upon which it probably opens^ 



