686 Laura Florence 



is raised in a ridge along the dorsal median line (Plate LXI, 4). The cutic- 

 ular strands coming from the now more widely separated dorsal ends 

 of the halves of the pumping pharyngeal tube are at first strongly chitinized 

 and pass laterad to the edges of the arms of the buccal plate, where they 

 turn ventrad and surround the sheath as a basement membrane to its 

 epithelium. The inner cuticula of the sheath is continued upward to the 

 ventral ends of the pumping pharyngeal tube as shown in Plate LXI, 3, 

 but the strong chitinization in the region of the dorsal piercers extends 

 farther dorsad, and the points passing around their lateral edges are less 

 curved downward. The gradual movement centrad and ultimate fusion 

 of these points cuts off the piercers from the pumping pharyngeal tube. 

 At the same time the strong chitinization continues dorsad until it fuses 

 with the ventral ends of the pumping pharyngeal tube, which gradually 

 move apart. In this wa}^ the pumping pharynx is formed, which, at 

 its anterior end, has the ventral surface much narrower than the doreal 

 (Plate LXI, .5). The cuticula coming from the dorsal ends of the pumping 

 pharyngeal tube is thick and strong, and fuses with the lateral edges of 

 the arms of the buccal plate, which are here elevated knoblilce and form a 

 firm base for the insertion of the dorsal protractor muscles (Plate LXI, 4). 

 From their lateral edges the thin cuticular layer still extends downward 

 to surround the epithelium of the sheath. The floor of the pimiping 

 pharynx graduall}'' broadens and assumes a rounded shape (Plate LXI, 6). 

 In only two areas — those of the insertion of the two large pairs of dilator 

 muscles — is there any strong chitinization of the dorsal wall of the pmnp- 

 ing pharynx. Just Ijchind the anterior area and after the floor has become 

 rounded, the pumping pharynx and the divert iculmn become entii-ely 

 separated from each other, and a short distance behind this separation 

 the chitinization of the ventral wall becomes stronger and that of the 

 lateral walls less strong (Plate LXI, 7). The dorsal waU only is capable 

 of dilation, and in the figures is seen in a resting condition. At the level 

 of the antennae the ventral surface narrows somewhat and a stronger 

 chitinization is evident throughout the structure as it passes mto the 

 pharynx. Also at the level of the antennae there apjjears the anterior 

 part of the plate imbedded in the floor of the sheath, which becomes 

 chitinized and l)ent to form a central furrow. The circular muscle of 

 the pharynx is well develoi^cd and surrounds the anterior part as a sphincter 

 (Plate LXI, 8j, but in no case has a transverse section of the pharynx 



