20 Annals Entomological Society of America _[Vol. VII, 
From a study of these two forms it seems probable that the 
galls which they form are not due to any product poured forth 
by the Malpighian vessels, for these neither secrete a fluid when 
in contact with a foreign substance, nor do the cells show any 
divergence from the normal type. 
The Malpighian Vessels of Other Hymenoptera. 
Since we have only considered species which form galls or 
are associated as parasites and inquilines with the gall-maker, 
it is necessary that we study related species that do not form 
galls, in order that this comparative study may be more com- 
plete. For this purpose we have selected species of Braconids 
and Ichneumons. 
A Braconid larva was obtained from the fall-webworm. 
A longitudinal section of this larva is shown in Fig. 67, Pl. IX. 
The cells of the Malpighian vessels are medium in size, and the 
nuclei irregular. They are equal to those of the tubules of the 
Chalcids, and larger than those in the vessels of the inquilines. 
The Ichneumon larva was secured from the red-humped 
apple-worm. Sections through the Malpighian tubules showed 
that the cells were small and regular, the nuclei round. Here 
we have a tubule the cells of which correspond in size to those 
found in the tubules of the inquilines. 
The Degeneration of the Larval Malpighian Tubules. 
The degeneration of the larval tubules, and the development 
of the adult vessels in the forms studied, are of such interest 
that, though in part discussed by Rossig, they may here be 
considered, and especially since the stages missed by Rossig 
can be supphed. 
Degeneration of the larval Malpighian tubules commences 
in the prepupal stage. The cytoplasm shows huge vacuoles, 
appears in shreds, and clings to the cell wall. The nucleus 
becomes greatly elongate and branched, and chromatolysis 
sets in. About this time small evaginations appear in the 
hind-intestine, which develop into cylindrical tubules. Grad- 
ually the cells of the larval Malpighian vessels break down, and 
pass into the lumen of the hind-intestine, while the adult 
tubules with small cells, and regular nuclei elongate rapidly. 
