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1914] Digestion and Digestive Epithelium in Insects 315 
In Fig. 11 we have in section a portion of the epithelium of a 
larva that has just molted. Here the large, loosely composed 
cells are not in evidence, and many of the small basal cells have 
grown out until they reach the intima. The other type of cell 
is present also, but is not shown in the drawing. The nodules 
projecting from the cells here and in Figs. 9 and 10 are interest- 
ing in that they seem to have pushed through the intima in- 
stead of having stretched it as appears in Fig. 7. They may be 
artifacts, or more likely they are drops of digestive fluid, such 
as van Gehuchten has described and figured in Ptychoptera, 
though I have never found them floating free as he has shown 
them. 
The larva of Dendroctonus, a Scolytid beetle, which bur- 
rows into the living wood of pine and other coniferous trees, 
affords a good example of an insect which feeds continuously, 
and hence must possess digestive cells which gradually and 
continuously pour out their secretions. Here the cells are 
exceedingly regular, each one like the next. There are no nidi 
to be seen, and no protruding portions are present. The 
secretion evidently oozes gradually through the intima in small 
droplets. The only good preparation that I have shows the 
basal half of these cells to be very compact and darkly staining 
while the distal half is open and loose. The nuclei are situated 
just at the bounadry between these two halves of the cells. 
This particular larva appears, to judge from the condition of 
the cuticle, to be upon the point of molting, and this division 
of the cells may be similar to that which Folsom and Welles 
have described in Collembola. 
The digestive epithelium of the Coccide, as represented by 
Lecanium, is very simple (Fig. 4). It consists of a row of more 
or less regular cells, with here and there one which is greatly 
enlarged. These large ones are evidently the active, secreting 
cells, while the smaller ones are developing. Frequently these 
contain two nuclei, indicating that they are formed by direct 
division. It would be interesting to see what happens to these 
cells at molting time, but as the Lecaniums only molt twice 
(Quayle), and these moltings come while they are still quite 
small, it would be rather difficult to get preparations. 
The digestive phenomena of various insects have been 
mentioned above briefly and I now propose to take up in order 
