GLAND STRUCTURE, ^ 
117 
nucleated cell layer, and the intima {x). With a high 
magnifying power, the intima appears dotted, from 
pores through which, Schiemenz says, possibly the 
secretion passes into the sacs. On leaving the sac, 
the several ducts become creased and striped, and 
gradually develop into tracheal-like tubes. 
The structure of this gland in the queen is similar, 
but larger, the cell layer being very much broader and 
more fully developed. In the drone this gland con- 
sists only of large masses of opaque yellow fat cells. 
These are the degenerated secreting cells. 
System III. 
Following the main duct (which has been described 
in System IT), we find it passing under the oeso- 
phagus into the front part of the thorax, and branch- 
ing off on either side. Very soon the tubes expand 
into a reservoir (Fig. 50, d, r), which is shaped like 
a sac, having at its extremity two ducts leading in 
opposite directions. One of these travels towards the 
oesophagus, whilst the other takes a direction in front 
of the wing muscles. 
The spiral structure of the intima of the main duct 
changes in the reservoir (d, r) to a membrane having 
star-shaped depressions. The ducts leading out of 
this have again a spiral structure, and the glands at 
the end are worm-shaped (Fig. 50, d, s) having con- 
strictions along the intima of the central duct, on 
which is situated a layer of cells. This cell layer is 
continued over all the ducts, as well as the reservoir. 
Although this cell layer is very thin, over those in the 
