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 déwnward. ‘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 way the pumping pharynx is formed, which, at 
its anterior end, has the ventral surface much narrower than the dorsal 
(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 knoblike 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 pumping 
pharynx gradually 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 pump- 
ing pharynx. Just behind the anterior area and after the floor has become 
rounded, the pumping pharynx and the diverticulum become entirely 
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 wall 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 into the 
pharynx. Also at the level of the antennae there appears the anterior 
part of the plate imbedded in the floor of the sheath, which becomes 
chitinized and bent to form a central furrow. The circular muscle of 
the pharynx is well developed and surrounds the anterior part as a sphincter 
(Plate LXI, 8), but in no case has a transverse section of the pharynx 
