216 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.39. 



larger female larva (fig. 33), we find that the digestive canal traverses 

 the entire length of the body, its two openings being virtually 

 terniinal. 



The mouth-tube is turned forward and its tip projects in front of 

 the frontal margin, making it the most anterior portion of the body. 

 Through its center runs the slender thread-like oesophagus (oe.) 

 which extends back opposite the base of the second maxillae without 

 any turn or sharp bend. There it passes abruptly into the enlarged 

 stomach, entering the center of the anterior end in the male and the 

 anterior ventral corner in the female. At the point of junction a 

 thick sphincter muscle (sm.) is formed, which projects strongly into 

 the stomach (s). The latter is completely fused with the intestine 

 so that it is impossible to distinguish any point of separation. Both 

 possess thick walls made up of an outer serous membrane, set with 

 nuclei and serving as the point of attachment for the numerous fibers 

 and muscles which suspend the tube within the body cavity, a median 

 muscular layer which produces the peristaltic movements, and an 

 inner glandular layer composed of large cells, whose darkly pig- 

 mented contents are gathered around a much lighter nucleus. Some 

 of these cells project into the stomach cavity much farther than 

 others, and their inner free ends are filled with a digestive secretion, 

 as evidenced by differential staining (gc.) . In the male the intestine 

 stops abruptly at the anterior margin of the last (abdominal) body 

 segment. The entire abdomen beyond it is filled with a plug of 

 loose cells and muscle fibers, through the center of which may be 

 seen the proctodeum (pc.) in process of formation. But it is not yet 

 finished and the anus has not broken tlirough, the posterior walls of 

 the abdomen being entire. 



In the female larva, however, the posterior portion of the digestive 

 tract is fully formed; otherwise there is no difterence in this region 

 between the sexes. At this early stage the body cavity around the 

 digestive tract is open save for the grouping of cells in various places 

 to form the beginnings of other organs. Through the wide spaces 

 thus left the blood can circulate freely. 



FRONTAL GLAND. 



In the anterior portion of the head, dorsal to the oesophagus, is the 

 large secretory gland which formed the attachment filament in pre- 

 vious stages (fg.). The filament itself is gone, and the peg or attach- 

 ment end has been torn out, leaving a gaping hole filled with a plug 

 (p) made of the secretion of the gland. This furnishes the final proof 

 of the transference of the filament from the frontal margin to the tips 

 of the second maxillfe. Claus thought he discovered the remains of 

 the peg in the head of the larva which he has figured, but he was 



