98 MCMURRICH. [Vou. XIV. 
counting the number of cells seen in transverse sections. This 
I have done with specimens of three ages; the youngest had just 
been set free from the brood pouch, and the other two were the 
4 mm. and 12.5 mm. specimens, from which the measurements 
were made. The number of cells found in a transverse section 
of each of these is as follows: 
Just set free 4 mm. 12.5 mm. 
33 30 38-40 
The figures do not agree absolutely, but since the smallest 
specimen has a greater number of cells than the 4 mm. one, it 
is quite probable that the differences are individual differences 
and do not denote an increase in the number of cells in the 
intestine as the individuals grow older. 
The evidence, then, which I have presented, though not 
absolutely conclusive, points very strongly, it seems to me, to 
the supposition that the increase im the size of the “midgut” 
of the land Isopods is not due to an increase in the number of 
cells, i.e., to cell-division, but to an increase in the size of the 
cells present at the close of embryonic life. 
The last part of this statement is an anticipation, and brings 
us to the question of regeneration. I have nothing to add to 
the discussion as to whether regeneration can take place by 
amitosis, but may simply state that I do not believe that regen- 
eration occurs in the forms which I have studied. In the first 
place, the gradual increase in the size of the “midgut” cells as 
the animals grow older does not favor the idea that the cells 
are thrown off from time to time and replaced by new ones, 
and in the second place regeneration is usually associated with 
cells which possess a glandular function, and of these there is 
not the slightest trace in the Isopod “ midgut.’ Ziegler and 
vom Rath (91) describe mitoses at the beginning of the “ mid- 
gut’? of an adult Azzlocra, and regard them as producing 
regeneration; but before this idea can be accepted it must be 
shown more definitely that these mitoses are not associated 
with the regeneration of the cells of the liver caca, and, 
furthermore, it must be shown that the region in which they 
were found was really the ectodermal “midgut” and not a 
