Marshall—On the Anatomy of the Dragonfly. 
767 
the folds are followed around the intestine it is seen that, be¬ 
fore making the entire circumference, nearly all of them either 
come to a sudden end or branch. At the anterior end the 
folds are smallest and are continued over that portion of the 
mid-intestine which takes part in the formation of the’ oeso¬ 
phageal valve (fig. 22). Over most of the mid-intestine, ex¬ 
cept at either end, there is often a smaller secondary fold on 
the apex of the primary ones (fig. 23). 
Throughout the entire extent of this region of the alimentary 
tract there are, except in the nidi, no great histological dif¬ 
ferences ; the size and form of the cells change on account of 
the folding of the wall. There is but a slight development of 
the circular and longitudinal muscular layers. The epithelial 
cells are long and narrow (fig. 24), becoming shortest at the 
regions of the secondary folds. The striated layer, rhabdorium, 
is present; at some places it contained a number of vacuoles 
but, as the dragonflies were taken at a period of inactivity, but 
few of the peculiar appearances due to secretory activity were 
seen. 
Over the entire mid-intestine nests of cells, nidi, are very 
noticeable (fig. 25) and are remarkable for their great abund¬ 
ance. The structure here is very similar to what has been 
described in the dragonfly nypmph, Sadones (24), Needham 
(14). All the dragonflies studied were caught during a day or 
two of unusually cold weather and had all been without food 
for some time; this tended to retard the secretory activities 
of the digestive tract. Specimens dissected showed the entire 
fore-intestine empty and in a large majority the same condition 
prevailed in the anterior part of the mid-intestine. Needham 
(14) found that within about an hour after feeding the discharge 
of the cells in the anterior part of the mid-intestine commenced, 
to be followed a little later by the more posteriorly situated 
cells. The adult dragonfly, as well as the nymph, is a great 
feeder and the conditions relative to this discharge would be 
as apt to occur in the former as in the latter stage. 
Hind-intestine. A dorsal view of the ileum shows an i ir¬ 
regular longitudinal folding of the w.all, extending from end 
