MECHANISBI OF SUCTION IN SCHIZONEURA LANIGERA. 319 



which the large pump-mnscle, p.m.^ is attached. This muscle when it 

 contracts pulls out the proximal wall^ thus enlarging the pump-chamber, 

 but in sections the muscle is always seen in the relaxed condition and the 

 pump-chamber is considerably reduced in size, and difficult to see. 



Tha immp-stemiB attached at its distal end to the wall of the hypopharynx. 

 It is compressed laterally, figs. 12-13. Two strong arms ol: chitin extend 

 from it laterally and fuse with the lateral walls of the hypopharynx, thus 

 affording- a firmer support for the pump. 



A minute canal (figs. 12 and 13, s.ed.'),i\\Q efferent salivary canal, extends 

 through the dorsal part of the pump-stem, along which the saliva is con- 

 ducted into the ejector canal, e.c, formed by the junction of the maxillary 

 stylets. 



The efferent salivary canal is continued beyond the pump-stem along the 

 ventral wall of the small hypopharynx lip, being enclosed by this wall, and 

 extends to its pointed extremity (figs. 1 and 10-13, s.ed.), where it is con- 

 tinued into a small chitinous process. A similar process extends from the 

 dorsal wall of the lip. There is thus formed a " V "-shaped cleft at the 

 extremity of this structure, as is shown in fig. 25. As will be shown later, 

 the dorsal process forms the continuation of the pharyngeal canal, which 

 leads into the suction canal formed by the maxillary stylets. Similarly the 

 ventral process enclosing the efferent salivary canal leads into the ventral or 

 ejector canal formed by the maxillary stylets. 



The salivary glatids * are situated above the oesophagus, and lie obliquely 

 partly in the prothorax and partly in the posterior region of the head, one 

 pair on each side of the median line. The salivary duct from each pair passes 

 beneath the thoracic ganglia, and both meet in the median line at the infra- 

 posterior region of the fore-head, where they form a bulbous expansion, c.s.d. 



From this structure a single median salivary duct passes forward into the 

 fore-head. It becomes greatly reduced in size, and extending in the median 

 line beneath the salivary pump^ turns upwards, forming an " S "-shaped 

 flexure, and enters the pump-chamber at the post-ventral end of the 

 pump-cylinder, as is shown in fig. 1. 



At the place of entry of the salivary duct into the pump-chamber, the 

 walls are so arranged that they exert a valve-like action^ the opening beino- 

 controlled by two smair bands of muscles, the ventral 'ptmip-muscles, v.m., 

 figs. 1 & 2, and figs. 15-18. These muscles are attached, close together, 

 to the wall at the place of entry, and extend backwards below the large 

 pump-musckj becoming attached to the ventral rods of clritin. The lumen 

 of the salivary duct is extremely small. 



The exit opening from the pump-chamber is situated at the antero-dorsul 

 end of the cylinder (fig. 1), and leads into the effWent salivary canal, 

 described above as passing through the pump-stem. 



* For further description of the salivary glands see Quart. Journ. Micr. Sci. vol. Iviii. 

 (1913) p. 680. 



