104 MCMURRICH. [VoL. XIV. 
examined; and although I repeated this experiment many times 
and found in every case the intestine filled with cochineal, yet 
never did I find the slightest trace of its absorption by the 
“midgut.” On the other hand in every instance the liver czeca 
were strongly tinged by the cochineal. 
_These results show that the “midgut” of Armadillidium does 
not possess an absorptive function; it merely serves for the 
passage of undigested material to the exterior. Digestion and 
absorption are both performed by the liver ceca, and appar- 
ently by them alone. I do not intend to review here the some- 
what voluminous literature on digestion and absorption in the 
Invertebrates, but will merely point out that Cuénot (92) has 
obtained results concerning the process of absorption in the 
pulmonate Molluscs identical with those I have just described 
for Armadillidium. 
A fact interesting in connection with these results is the 
complete absence of a ‘midgut ”’ (and rectum) in certain para- 
sitic Isopods, and its great reduction in others. Thus in the 
Bopyridze, according to the observations of Kossmann (81) on 
Bopyrina Virbzz, the intestine, behind the point where the liver 
caeca communicate with it, is very narrow and possesses only 
an exceedingly fine lumen. On the other hand, the two liver 
caeca are very large,—in fact they might be described as large 
pouches, and they communicate with the intestine by such wide 
mouths that it is proper to speak of the presence of a true mid- 
gut in these forms. Kossmann says: ‘‘Dass durch den Mittel- 
darm Nahrung—und wir miissen ja hier an fliissige denken — 
direkt inden Enddarmtreten k6nne, ohnezunachst die Leberhohl- 
raume so gut wie vollstandig zu erfiillen, ist offenbar unméglich.” 
This arrangement seems to me at once comprehensible if the 
physiological actions of the liver and the intestine are as I have 
supposed them to be in the terrestrial Isopods. In parasitic 
forms the amount of fecal matter is relatively very small, while 
the amount of material to be absorbed is large. The intestine, 
not being absorptive but merely serving as a passage for the 
extrusion of the undigested material, is, in Bopyrina, exceed- 
ingly reduced, while the digestive and absorptive liver pouches 
are enlarged. 
