Life-history of Phalacrocera replicata. 35L 
enlar cavity. The glands are widest behind, and here 
the lining epithelium almost disappears, so that the 
glands become converted into mere reservoirs; they 
taper forwards, and pass into ducts, which unite below 
the suboesophageal ganglion to form a slender common 
duct, which enters the floor of the mouth (figs. 10, 18a.) 
Malpighian tubules (figs. 18a, 18h). There are four long 
Malpighian tubules, which open at the junction of the 
stomach and intestine. Hach passes forwards nearly as 
far as to the cesophageal invagination, and then turns 
backwards, ending opposite the colon in a_ coiled 
extremity. 
3. The heart of the larva. 
The heart (fig. 18a,18b) lies in a pericardial space, which 
is cut off from the body-cavity (hematoccel) by the usual 
diaphragm. he pericardial cells and alary muscles 
present no uncommon features. In the hinder part of 
the heart are several pairs of valvular inlets. There is 
one feature of the heart which we have never met with in 
any other insect, nor do we know of a close parallel in 
any other animal. ‘lwo cellular cords he free in tke 
cavity, which they traverse from end to end. They are 
attached behind to the body-wall between the spiracles, 
and extend forwards as far as the brain. They are 
here and there attached tothe wall of the heart by slender 
threads. The cords are cylindrical, and consist of a 
transparent, slow-staining substance, in which are im- 
bedded innumerable quick-staining cells, with relatively 
large nuclei(figs. 24-26). The cells are irregular, and often 
branched ; between them and towards the centre of the 
cord is an irregular but probably continuous cavity. We 
are inclined to think that this cavity is filled in the hving 
larva with a fluid, perhaps with blood. Sections reveal 
the very unexpected fact that the cords are of epidermic 
origin, tubular extensions of the epidermis of the hinder 
end of the body. They appear to pass into the heart 
through a pair of opening's in its posterior wall.* 
In the pupa the cords become beaded, break up, and 
finally disappear altogether. The difficulty of investigat- 
ing the details of the process is very great, owing to the 
** Owing to the great transparency and delicacy of the wall of 
the dorsal vessel, the double opening which we have mentioned 
was not clearly seen. 
