254 
F. G. HEATHCOTE. 
exterior by a narrow neck and two lateral recesses opening into 
the neck and placed ventrally to the main sac parallel with the 
ventral surface of the head. The section C taken through the 
median portion of the organ exhibits similar relations, excepting 
that the median dorsal wall of the sac is projected into the 
interior in two longitudinal folds which make a partial division 
of the sac into three portions, two deep, wide lateral pouches, 
and one deep narrow recess between them. This latter I shall 
speak of as the median recess. A third section, D , is taken 
through the hinder part of the organ. Here the lateral 
recesses and the slit-like opening to the exterior are absent 
and the two dorsal folds almost completely divide the main 
sac in three portions. 
It is worthy of note that the effect of the median and lateral 
recesses is to produce a freely projecting lip or edge on the 
dorsal and ventral aspects of each pouch. 
The general shape of the interior of the organ is therefore 
posteriorly that of two pouches projecting into the interior of 
the head, while between them is a median dorsal recess formed 
by the folds above described, which constitute the inner walls 
of the pouches where they approach one another. Anteriorly 
the division into two pouches is not so perfect, but there are 
two deep lateral ventral recesses. The slit-like opening to the 
exterior begins at the anterior end and extends about a third 
of the length of the whole organ. 
The chitinous exoskeleton is continued into and lines the 
whole organ. It is not, however, of uniform thickness. In the 
median and lateral recesses and on the folds constituting the 
lips of the pouches it is smooth, but in the pouches themselves 
it is thrown into a number of folds and bears a large number 
of chitinous hairs (fig. 2, h .) which project into the lumen of 
the pouches. The folds form alternate ridges and depressions, 
so that when looked at from the surface through a microscope 
the chitinous lining of the pouches has a reticulated appearance 
(fig. 8). The hairs, whose length is about that of the diameter 
of each pouch, are of peculiar form (fig. 9). Each consists of 
a stout elliptical basal portion, the inner end of which is inserted 
