116 PROBOSCIS AND THARYNX— MUSCULATURE. 



strip. When the pair of muscles referred to (m'') are contracted, 

 this strip functions as a hinge ai-ound which the pharynx moves 

 in a downward direction, and the result is that the lower end of 

 the pharynx, whicli by its apical tube (Fig. 21, 7i;) is united with 

 the base of the external mouth-parts, is forced downwards, pulling 

 the external mouth-parts in the same. direction and extending the 

 nuMubranous cone between these mouth-pai-ts and the firm chitin 

 of the head. The cone is retracted by at least three pairs of 

 muscles. One pair (Fig. 21, »w^) is inserted on its posterior wall 

 below the firm chitin, and proceeds upwards to . a spot outside 

 the occipital foramen ; the second pair of muscles (7*1'') proceeds 

 upwarils from the proximal end of the lower wall of the labium 

 to the firm chitin on the posterior side of the head ; the third 

 pair (»i-) runs from the sub-apical part of the apoderaes of the 

 labium upwards and backwards to the posterior side of the head 

 outside the occipital foranuMi. Probably a fourth muscle 

 (Fig. 21, ?«*), proceeding from the proximal end of the upper 

 wall of the labrum to the anterior margin of the pharyngeal 

 wings, may also act as a retractor of the membranous cone, and 

 also as a depressor of the labrum, as mentioned above. That 

 the tlu'ee first-mentioned pairs can act as retractors of the cone 

 is certain, but I must confess that I do not know whether tluey, 

 or at least some of them, have some other function in addition. 

 The muscles (Fig. 21, vi^) from the free end of the apodemes of 

 the labrum to the lower end of the pharynx can certaiidy not 

 only act as mentioned above, viz. raise the distal end of the 

 labrum, but also assist (»t^) by the evagination of the membranous 

 cone. 



It has been mentioned above that the hypopharynx forms the 

 outlet for the saliva from the glands in the thorax. The hypo- 

 pharynx (Fig. 22, c) is perforated near its base on the under 

 side, and from this aperture begins the free salivary duct (/*), 

 which runs upwards along the posterior side of the most distal 

 part of the pharynx, and then (i) turns in a more backward 

 direction to the occipital foramen. Just behind the sub-apical 

 solid part of the pharynx the duct is dilated, and in the normal 

 condition depressed into a sort of oval disk, with the anterior 

 wall a little concave and the posterior convex. (In the specimen 

 drawn in Fig. 22 this organ, k, was unusually thick, the anterior 

 wall being raised.) From the anterior wall proceeds a pair of 

 very thin and long muscles (Fig. 22, m ; Fig. 21, m^), the other 

 extremity of which is attached to the posterior surface of the 



