No. 428.] THE METAMORPHOSIS OF SISYRA. 625 
degeneration which is characteristic of the first stage of meta- 
morphosis. Sections of older larvae show the silk glands in a 
much more advanced stage of degeneration, and numerous 
leucocytes in their vicinity or 
clinging to their walls. Inthe 
pupz there are only a few frag- 
ments of the larval silk glands, 
but adult Malpighian tubules 
are seen forming, for which the 
material from the degenerated 
silk glands is probably again 
used. 
Digestive Epithelium.— 
Sections through the digestive 
epithelium of a normal, feeding 
larva show vacuolization, even 

n showing gradual m 
fi n into silk-secreting cells ; e, longitudinal 
section of silk gland, showing vacuolization. at this early stage At the 
anterior end of the stomach is a circular band of small cells 
which remain active and functional during the period of degen- 
eration of the other epithelium. In the process of pace 
all traces of cell boundaries disappear, in some 
places the cell substance being a liquid mass 
in which float the nuclei. The disintegrated 
epithelium is finally cast off from the walls 
into the center of the cavity and the new 
rapidly grows out from the regenerative band 
to take its place, new nests of regenerative 
cells appearing at frequent intervals. It would 
seem that the solid cord of cells at the poste- 
rior end of the stomach serves as another 
regenerative center, since at this stage there 
is an opening from this end of the stomach pepe 

— Larval wing. 
A,hypodermis; 2, 
through what was the solid cord in the larva.  peripodal membrane ; 
The adult intestine seems to be developing ^A% * whs 
from the cells at this point as a regenerative center. The adult 
Malpighian tubules are probably also developed in part from these 
cells. I have seen clear evidences of a new set of these organs 
forming in the normal position at the base of the stomach. 
