THOMPSON: METAMORPHOSES OF HERMIT CRAP. 
163 
gut in the rear of the thorax, turns back into the abdomen and lies 
there in a coil superficial to the livers (pi. 8, fig. 46, ic). The chiti- 
nous gut near the point of union with the anterior gut has the usual 
series of prominent folds, the methoria, and at its posterior end a 
rectum is differentiated. This occupies the sixth segment and the 
telson. 
In the zoea and glaucothoe phases the achitinous gut is longer 
than in the adult and extends back to a point within the fifth seg¬ 
ment of the abdomen, where its short, columnar cells give place to 
the larger, more vacuolated cells of the chitinous gut (pi. 9, fig. 54, 
c/i int). Methoria are present at this point with the glaucothoe and 
during the latter part of this period the unpaired caecum arises as an 
outpushing of the dorsal wall of the achitinous gut just cephalad of 
these folds. As soon as this diverticulum appears, or occasionally 
a little earlier, the chitinous gut begins to encroach on the territory 
of the achitinous gut. Unfortunately, however, sections throw no 
light on the mechanism of the change, but a series of specimens 
merely shows the caecum, methoria, and chitinous lining lying 
farther and farther forward in the abdomen, until with the earlier 
adolescent stages the methoria reach their definitive position in the 
region of the second segment. No mitotic figures can be found and 
although histolysis occurs at this time throughout the length of the 
gut, it is not especially prominent. 
The elongation of the achitinous gut which brings the proximal 
end of the caecum from the abdominal into its definitive thoracic 
position, must take place late in adolescent life. The diverticulum 
was still wholly abdominal in a reared specimen two months past 
the glaucothoe. But some small crabs that were collected at 
Wareham, Mass., in August, 1900, showed the caecum in its definitive 
relations. The asre of these crabs was not known, but thev were 
very small and their development was greatly advanced over that 
of larger, reared crabs known to be sixty days past the glaucothoe 
phase. So they were probably about a year old ; perhaps two 
years old. 
An elongate achitinous gut which is gradually replaced by the 
chitinous gut, is found in the young of other Decapods besides 
Eupagurus. For these, however, I have only fragmentary records. 
An examination of an immature Yirbius, 4 mm. long, and of a 
Crangon with a length of 6 mm., shows no methoria, but the 
