35 



trough, in the hollow of which is the labrum-epipharynx (lr-e) with the hypo- 

 pharynx (A) closely pressed beneath it. A cross-section of the same proboscis at 

 fi (figured in /?'), fig. 1, reveals the bases of the maxillary palpi (>np) above, and 

 within the proboscis a section of the distal half of the fulcrum, which contains 

 the pharynx Q>) and the pharyngeal muscles (pin). At each side of the pharynx 

 is the section of a chitin-piece (x) and its surrounding muscle, the functions of 

 both of which will be discussed later ; directly beneath the pharynx, in the median 

 line, the salivary duct (sd) is sectioned. If a section of the fulcrum be made 

 still further toward its proximal end, its upper side will be found to be closed 

 .together, as in fig. 4. 



The labrum-epipharynx of Musca vomitoria is a little longer than the hypo- 

 pharynx, tapers gradually from base to tip, is strongly chitinized, is clothed with 

 fine short hairs on the upper surface of its basal half, is- in cross-section through 

 the middle (fig. J , a', lr-e) shaped like a horse-shoe with both its aides broadened, 

 and is composed of a labrum and epipharynx, separable from each other in caustic 

 potash. From the labrum to the epipharynx, in the basal half of the labrum- 

 epipharynx, extend muscles. The extreme tip of the labrum-epipharynx has the 

 shape of a quill-pen with its point evenly rounded off, is very thin and transparent, 

 and is lined on its inner side with numerous very fine short spines. The base 

 of the labrum-epipharynx is jointed to the distal end of the fulcrum in such a 

 manner that the labrum is continuous with the upper surface (fig. 1, /?', <') of 

 the basal half of the proboscis, and the epipharynx with that portion of the 

 fulcrum which directly covers the pharynx dorsally. The tip of the labrum-epi- 

 pharynx is so completely surrounded by the sides of the labium, which, at the 

 point where the labrum-epipharynx ends, are so developed dorsally as to form a 

 tube, that the fly. itself probably cannot raise the labrum-epipharynx out of the 

 trough of the labium. The two can be separated, however, with a pair of needles 

 without tearing the parts, if the operation is performed very carefully. 



The hypopharynx of Musca vomitoria (fig. 1, a', h, in section) is thin, tapering 

 gradually from its base to its tip, which is acute and sparsely clothed with very 

 fine hair. The basal portion of the hypopharynx contains a tube, which opens 

 into a groove on the upper side of the distal half of this organ; this tube is 

 the outlet for the saliva, which is conducted to its basal end by a duct which 

 has rings similar to those of tracheae. The course of this duct is shown by the 

 dotted line sd, on figs. 2 and 3, and its position, in section, at sd of fig. 1, /?'. 

 The hypopharynx lays closely pressed to the under side of the epipharynx, from 

 which it is not always easily separated, and with which it forms the tube for the 

 passage of food to the pharynx. The base of the hypopharynx unites beneath 



