424 THE ALIMENTARY CANAL OF THE IMAGO. 
not a prior stage, and that if such a discontinuity is estab- 
lished, which I think possible, so far as the lumen of the 
alimentary canal is concerned in the Hymenoptera and some 
Diptera, it only occurs after the larva ceases to feed ; and it is 
probable, I think, that the peculiar modification in the histo- 
lytic process which I have described in the Blow-fly nymph 
depends on the great length of the narrow hind-gut of the 
larva. It is easy to understand that the expulsion of the 
remains of the metenteron may be effected where it is a short 
wide tube, as it is in the Hymenoptera, by the anus. 
There appears to be little doubt that the anal extremity of 
the intestine is closed in the Bee larva, during all the earlier 
stages of its development; and this is inconsistent with the 
view that it is developed from a proctodzal involution. At 
least, it is quite as likely that a secondary closure of the com- 
munication between the chyle stomach occurs as that the 
intestine becomes blind—as it almost always is at its anal 
extremity in the embryo insect—if it is really developed from 
a capacious proctodeeum. 
I suspect the received view originated from the following 
statement of Weismann [2, p..74]. He says: ‘As the blind 
ceecee are developed from the anterior end of the mid-gut, so 
the Malpighian vessels arise from the anterior end of the hind- 
gut. But,’ he adds, ‘I have seen no earlier stages which sup- 
port this view, yet I think it must be accepted, as it is supported 
by histological structure.’ 
Weismann gives a figure in which he represents the mid- 
gut, with the Malpighian tubes growing from a mass of cells 
which are continuous with its wall. He also represents both 
the intestine and the tubes as solid, and in another figure he 
shows the posterior end of the stomodeum as a solid mass of 
cells. 
I have made numerous sections of embryos in this and in 
earlier stages of development, and have invariably found both 
the Malpighian tubes and the intestine hollow. I can quite 
understand the difficulty which Weismann laboured under, as 
he had to rely entirely on dissections, and it is impossible in 
