DEVELOPMENT OF THE ALIMENTARY CANAL. 423 
anterior extremity, and a mesenteron which is a wide sac 
opening only by the cesophagus, and entirely disconnected with 
the proctodeum, which terminates in front in the four large 
Malpighian tubes. This condition was described by Dohrn, 
k. Leuckart and others, who regarded it as an anterior stage 
of development to that described by Swammerdam. 
I have no doubt that the condition so described is a subse- 
quent stage characteristic of the resting larva. Dohrn says, 
“In many Hymenoptera the union of the hind-gut and mesen- 
teron only occurs at the end of the larval period. It may be 
observed that if a fairly full-grown Ant larva is hardened and 
cut through vertically, the mid-gut forms a sac, which is 
bounded by a layer of large cells, and contains within it 
about twenty cuticular layers enclosing a brown mass of fecal 
material; whilst the hind-gut forms many coils, and is often 
found to terminate in front in a blind end.’ I think it is clear 
that Dohrn was dealing with a resting larva or young nymph, 
as the conditions described are similar to those seen in the fly 
nymph (pronymph stage). The supposition that, in the feeding 
larve of the Hymenoptera, a blind mid-gut unites with 
the hind-gut after the functional activity of the organ has 
ceased, and just before the whole alimentary canal under- 
goes histolysis, is scarcely probable; on the other hand, it is 
extremely probable that, as in the fly nymph, the union between 
the parts of the alimentary canal becomes very narrow (see 
Pl. XXV., Fig. 1), or may even become a mere fibrous cord. 
It is possible that the whole of the Malpighian tubes and the 
metenteron are expelled through the short, wide intestine in 
the Bee nymph, and that the new metenteron and new Mal- 
pighian tubes are developed, as in the fly nymph, from the 
saccular mid-gut. 
Leuckart, in his great paper [20] on the development of the 
Pupiparz, does not represent the alimentary canal as discon- 
tinuous ; but in a previous note* he announced that he had 
discovered a similar want of continuity in the nymphs of these 
insects; again, I think he had to do with a subsequent and 
* Bull. Acad. Sci. Bruxelles,’ xxi, 1854, pp. 851, 852. 
