424 THE ALIMENTARY QANA.L OF THE LMAGO. 



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 proctodasal 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 proctodaeum. 



I suspect the received view originated from the following 

 statement of Weismann [2, p. 74]. He says: 'As the blind 

 catcae 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 stomodaum 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 



