ANATOMY OF. TUE GOUT-FLY OF BARLEY. 799 



is pioiluced laterally on each side into a fairly .stout suspensory 

 process (s.pr.) whose otlier end is attached to the surface of the 

 dorsal lobe of its side. These suspensory processes do not appear 

 to contain any nervous elements. The dorsal and lateral regions 

 of the ring are formed of fairly large cells, each with a single 

 large nucleus containing a hig, densely-stiiining nucleolus and a 

 few scattered chromatin granules. The ventral and posterior part 

 of the ring is composed of very small cells wdiich have exactly the 

 appearance of the cortical ganglionic cells. This region is un- 

 doubtedly a ganglion ; it becomes more prominent in mature 

 larvaB, in which it is marked off from the lateral regions of the 

 ring by a deep fissure on each side. A strand of tissue 

 (presiunably nervous) (p.n.) leaves this ganglion and passes back- 

 wards and downwards to the dorsal surface of the proventriculus- 

 where it forms a small ganglion (p.g.). Another strand (m.n.) 

 goes forward and downward from the ganglion and passes under 

 the transverse commissure uniting the dorsal lobes of the brain, 

 in front of which it breal<s up into four nerves which pass 

 forwa.rds to supply the avsophagus and pharyngeal mass. In the 

 l)low-11y larva, according to Lowne (13), the corresponding nerve 

 swells out to form a, small median ganglion just posterior to 

 the transverse commissure, and from this ganglion nerves pass 

 forward along the oesophagus, round which they form a plexus. 

 The median ganglion could tiot be distinguished in Chlorops. 

 From the posterior region of the transverse commissure a stout 

 vertical strand of a fibrous nature (I'.s.) passes upwards to be 

 inserted into the ventral wall of the dorsal vesssel. There is no 

 ganglion at its point of junction with the dorsal vessel and it 

 gives oft' no nerves; it is probably, therefore, pui-ely suspensory in 

 "function. The dorsal vessel passes forwards and, slightly anterior 

 to the transverse commissure, it fuses with the posterior region 

 of the cephalo-pharyngeal band in the manner described below. 



The dorsal cornua of the pharyngeal sclerite aie each sun-ounded 

 by hyporlerm, the hypodermal sheaths being united by a narrow 

 arched band of hypoderm, which is continuous anteriorly with 

 the hypodermal sheet which unites the dorsal margins of the 

 pharyngeal sclerite and which, as mentioned in the description of 

 the pharyngeal skeleton, is really a double sheet. The hypo- 

 dermal sheaths of the dorsal cornua are continued posteriorly 

 beyond the termination of the pharyngeal sclerite as hollow tubes 

 of" hypoderm (?'..s.j9.) united by the arched dorsal hypodermal 

 plate {c.p.h.). The hollow tubes are the peduncles of the cephalic 

 imaginal sacs and the arched plate is the cephalo-pharyngeal 

 band. The relationships of the parts ai-e most easily made out in 

 fairly young third instar larva? : in mature larva; the enormous 

 growth of the cephalic imaginal discs makes the interpretation of 

 sections somewhat more difRcult. In such a young larva the 

 peduncles of the sacs decrease rapidly in diameter as they pass 

 backwards and their cavity becomes practically obliterated. In 

 the third thoracic segment they increase in size to form the 



