250 Prof. L. C. Miall on Dicranota ; 
tral surface of the pupa. These are used to assist the 
movements of the pupa through the mud. They are not 
unlike the pseudopods of the larva, but bear no hooks; 
they are carried on corresponding segments. I find that 
a pupa extracted from its burrow and laid upon damp 
mud readily travels about, and in no long time estab- 
lishes itself in a convenient position just beneath the 
surface. 
As in many other aquatic Diptera, the pupa is notably 
smaller than the larva. In Dicranota it is only 2 in. 
long, about half the length of the larva. 
The Fly. 
I have only slightly examined the anatomy of the fly. 
The alimentary canal is less voluminous than in the 
larva, and most of the abdomen is occupied by the 
reproductive organs. The large gluten-glands of the 
female lead me to suppose that the eggs are enveloped 
in a slimy mass or egg-rope, and laid in water. 
Development of the Fly. 
As usual in Diptera, the external organs of the fly 
first become discernible in the larva, and originate in 
invaginations of the larval epidermis. I have observed 
nothing unusual in the development of the wings and 
legs. The invaginations for the imaginal head form on 
each side of the median septum of the larval head (see 
p. 238), and extend downwards around the csophagus. 
From these primary folds secondary invaginations for 
the mouth-parts are given off. The rudiments of the 
compound eyes form close to the septum, but on the outer 
wall of the invagination ; the rudiments of the imaginal 
antenne are behind them. The arrangements of the 
cephalic invaginations is considerably simpler in Dicra- 
nota than in Chironomus.* There is no folding-in of the 
larval epidermis at the junction of the head and thorax, 
and the invaginations extend backwards only for a short 
distance beyond the larval head. 
I have to thank my friend Mr. Hammond, of the 
Linnean Society, for making a number of drawings for 
* Miall and Hammond, Linn. Trans., 2nd series, vol. v., 1892, 
