No.1.) MUDGUT OF THE TERRESTRIAL ISOPODS:. 105 
This degeneration of the “midgut” is carried to its complete 
extent in the Entoniscidz, according to the observations of 
Giard ('7g) and Kossmann (gia), there being no continuation of 
the digestive tract beyond the point where the liver pouches open 
into it. Even though these forms are parasitic, it is difficult to 
understand the complete absence of the intestine if it be absorp- 
tive in function, since even in such forms as the Trematodes 
there is a necessity for a well-developed absorptive intestine. 
If, however, the intestine is not absorptive, then its disappear- 
ance in these cases of extensive parasitism is not remarkable. 
What, then, is the explanation of the curious structure of 
the epithelial cells and of the occurrence of the granules and 
vacuoles in them? I believe that al// the peculiarities are due 
to catabolic changes. I have stated on a previous page my rea- 
sons for the belief that the epithelial cells persist throughout 
the entire life of the animals; and I have shown that the devel- 
opment of the vacuoles, of the granular structure of the proto- 
plasm, and of the supportive fibres progresses with age. I regard 
these changes, therefore, as associated with the senescence of the 
cells. The fragmentation of the nucleus, not infrequently seen 
in fully adult individuals, and, indeed, the abnormal forms which 
the nuclei assume are very probably due to the accumulation in 
the cells of catabolic products, and I believe the granules which 
occur in Armadillidiwm are to be regarded as products of this 
kind, and that their presence indicates approaching dissolution. 
Such an opinion as I have here expressed may seem some- 
what at variance with the usual conception of an intestine, but 
I would point out that in the formation of the “brown body ” 
in the Ectoproctous Bryozoa we have something which may be 
regarded as to a certain extent analogous. Furthermore, it 
must be remembered that in the Isopods we have to do with 
an intestine which is in reality entirely an ectodermal procto- 
dzeum; and it would, it seems to me, be not only remarkable to 
find it assuming the functions of an endodermal gut, but also 
difficult to explain why it should do so when a well-defined 
endoderm capable of digestion and absorption is present. 
ANATOMICAL LABORATORY, UNIVERSITY OF MICHIGAN, 
September 5, 1896. 
