NOM NeelOGUL OF Tae TERRESTRIAL JSOPODS. 103 
imagine a structure whose function is to absorb nutrition, lined 
throughout on the surface which is in contact with the material 
,to be absorbed by a highly impervious layer of chitin? 
I was struck with this obvious discrepancy between the struc- 
ture and the supposed function of the “ midgut” early in my 
studies, and endeavored to test the accuracy of the supposition 
as to its function. These tests were conducted upon adult 
individuals of Avmadillidium, this form presenting, for the 
purpose I had in view, what I supposed was an advantage over 
the other genera. This was the occurrence in the epithelial 
cells of adult individuals of numerous yellowish granules, as I 
have already stated; it seemed probable, on the assumption that 
the ‘midgut’ was absorptive, that these granules might be 
products of assimilation stored up in the cells of well-fed speci- 
mens. The fact, however, that in many specimens kept under 
most favorable conditions for obtaining a plentiful supply of 
nutrition, the granules did not occur, opened up a way for 
doubt as to their being assimilation products, and to determine 
if this were their significance I caused a number of individuals 
to fast for varying lengths of time by keeping them in glass 
vessels, the air of which was kept moist by damp filter paper 
being attached to the cover of the vessels so that it could not 
be reached by the animals. Some individuals I allowed to fast 
for four days, others for seven, others for ten, and finally some 
for fifteen. In every case I obtained the same result as I had 
from well-fed specimens; the epithelium of some individuals 
contained the granules, and that of others none, and when the 
granules were present they were just as abundant as in the 
well-fed specimens. I concluded, therefore, that the granules 
could not be assimilation products, since, if they were, they 
would surely have been completely used up, or at least greatly 
reduced, before the expiration of a fifteen days’ fast. 
Before discussing further their significance, however, I wish 
to mention the result of feeding experiments, which I also tried. 
Individuals that had fasted for a few days were allowed to feed 
on powdered cochineal, which they devoured at first with avid- 
ity. As soon as the cochineal began to be passed from the 
intestine as faeces, the animals were killed and the “ midgut ” 
