10 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
walls have the characteristic granular vacuolated protoplasm and 
large nuclei. The lumen is ample and communicates widely with 
the lateral pvloric pouches of the stomach. In the first stages of 
development these glands are simple cylinders which extend forwaid 
beyond the oesophagus and backward into the potential thorax. 
The anterior and posterior ends are tapering. But in the third and 
later stages the region lying posterior to the stomach gives off a 
longitudinal series of lateral, and several dorsal diverticula. 
At the time of the moult to the adolescent phase a diverticulum? 
the intestinal caecum, arises from the dorsal wall of the achitinous 
gut just caudad from the methoria, which at this period lie farther 
forward than in the earlier stages. This caecum has a similar 
development in the genus Eupagurus, just forward of the methoria 
in the fifth abdominal segment; and, in this form, caecum and metho¬ 
ria lie farther and farther forward in successive stages until the lat¬ 
ter reach their adult position in the second abdominal segment and 
the caecum becomes thoracic. The mechanism of this change is not 
clear in either instance, and in Naushonia, of course, the definitive 
position of the methoria and caecum is not known. As the chiti- 
nous gut in Gebia and Callianassa is shorter than with most Macru- 
rous forms, it is possible that in Naushonia the methoria are only 
barely thoracic in the adult. 
Aorta, antennary, superior abdominal, and sternal arteries are 
present in all the stages. Hepatic arteries, however, are not devel¬ 
oped in preadolescent life. A similar retardation in the development 
of the hepatic arteries is found in Eupagurus, and Claus (’ 84 ) figures 
a well advanced larva of the Adriatic Thalassinid, Calliaxis, with 
antennary but without hepatic vessels. It seems to be more usual 
among Decapods, however, for both pairs of arteries to be developed 
at the same time. The antennary arteries give off branches to the 
antennae, eyes, and stomach (pi. 2, fig. 23). In the inysis stages at 
least, and in the earlier stages, there is an enlargement of the aorta 
near the base of the rostrum (pi. 2, figs. 21, 25). Segmental arteries 
from the superior abdominal, with the exception of those for the 
sixth segment, are found in all stages. Those for the sixth segment 
are first detected in fourth-stage larvae, but they possibly arise 
earlier. The ventral abdominal artery is unbranched. It was not 
possible to determine the arrangement of the ventral thoracic artery 
in the different stages, beyond tracing the main trunk to the region 
of the head in a fourth-stage specimen. 
