164 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
achitinous gut extends back as far as the fifth abdominal segment, 
A similar condition is found in Homarus even in the first adolescent 
— fourth — stage, at which time the animal is adult in form and has 
a caecum developed from the anterior gut. Among Thalassinids r 
the older zoeae of Geb'ici affinis and Callianassa stimpsoni have the 
union of the two regions of the gut in the fifth abdominal segment, 
and in all the preadolescent stages of ISTaushonia (M. T. Thompson,. 
:03) this relation is maintained with the addition of methoria. The 
metazoea of Hippa talpoidea has the methoria in the anterior part of 
segment five of the abdomen, but in the first adolescent these have 
moved to the second segment. Among the Brachyura, the late 
zoea of Pinnotheres displays the anterior limit of chitin at the fifth 
abdominal segment and the megalops has methoria at this point. 
There is no caecum at this stage. On the other hand, a very young 
zoea referable either to Cancer or to Carcinus showed methoria and 
a well developed caecum in the second abdominal segment. The 
megalops of Callinectes hastatus likewise has these parts in this 
anterior segment and in this crab they have moved to the first 
segment in the first adolescent stas:e. Cancer irroratus has the 
caecum and methoria in the rear of the thorax in both metazoea 
and megalops. 
The livers or enteric glands, which open from the lateral pyloric 
pouches are very voluminous in the adult crab. Each consists of an 
axial tube from which arise slender lateral diverticula. The latter 
are long and numerous along the abdominal portion of the axis, but 
short and scantv alonsr the thoracic. Both axis and tubules have a 
O 
wall of one layer of cells with abundant cytoplasm (pi. 9, fig. 53) 
vacuolated and laden with secretions. At intervals, single cells or 
groups of cells, either granular, or more usually vacuolated, project 
into the lumen and partly occlude it. Proper fixation of these 
tissues is difficult and they do not stain readily. 
Immediately caudad from the openings of the livers into the 
pylorus, a pair of lateral caeca arise. These he one on either side 
of the stomach in an irregular coil. The cells of their walls are 
distinguishable from those of the livers by the absence of secretions 
and vacuoles, and by the ease with which they may be fixed 
and stained. 
* 
During the zoea phase, the livers are cephalic in position (pi. 8, 
fig. 34-37). Each communicates with the pylorus by an extensive 
