528 C. GORDON HEWITT. 
distance from their origin they bifurcate and the resulting 
four tubules have a convoluted course, being mingled to a 
great extent with the adipose tissue. They are similar in 
appearance and histologically to those of the imago, consisting 
of large cells, of which only two can be seen usually in section ; 
they consequently give the tubules a moniliform appearance. 
In the mature larva these cells appear to break down to form 
small deeply-staining spherical bodies. This histological 
degeneration begins at the distal ends of the tubules, which in 
the mature larva usually have the appearance shown in fig. 28 
(m. t.); all the stages of degeneration can be traced out. 
This process may be a means of getting rid of the remaining 
larval excretory products. 
The four ceca at the anterior end of the qerackealins have 
already been described. 
5. Tae RESPIRATORY SYSTEM. 
The tracheal system (fig. 26) of the adult larva consists of 
two longitudinal tracheal trunks united by anterior and 
posterior commissures, and communicating with the exterior 
by anterior and posterior spiracles, the latter are situated in 
the middle of the oblique caudal end, and the anterior spiracles, 
which are not present in the first larval instar, are situated 
laterally at the posterior border of the third body-segment. 
I believe that the anterior spiracles (a. sp.) are true func- 
tional spiracles, though for some time I .shared Lowne’s 
opinion that they were not functional. This latter view was 
due to the fact that it was difficult to understand how these 
spiracles could obtain air when they are immersed, as they 
usually are, in the moist fermenting materials on which the 
animal feeds. A careful examination of their structure, how- 
ever, strengthens my belief that they are able, if necessary, 
to take in air; the occasions when this is ‘possible are 
probably not infrequent. Hach of the anterior spiracular 
processes consists of a fan-shaped body (fig. 9, a. sp.) bearing 
six to eight small papilliform processes. The papille (fig. 7) 
