152 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
water. This suggests a possible function for these appendages in 
both sexes to reinforce the current in the shell which is primarily 
induced by the branchial outflow and movements of the body. Bate 
(’50) records a similar movement of the appendages in female hermit 
crabs which were bearing eggs. The role played by the sensory hairs 
on these appendages must be nearly equivalent in both sexes. 
A large columella prominence is present. Although it has been 
suggested that this organ aids the crab in maintaining a firm hold 
on its shell, I feel that this cannot be a complete explanation for the 
existence of the structure. If it serves this function at all, it must 
be mainly passively, in conforming the body more perfectly to the 
columella angle of the shell chamber. Moreover, it is not a very 
muscular organ even in the genera in which it is well developed and 
it is only imperfectly developed in a large number of hermit crabs. 
Our species of Eupagurus maintain their hold on the shell chiefly by 
the grip of the calcified telson and uropods on the columella, 
while the tuberculated areas on the posterior thoracic limbs and 
uropods may lend assistance. The chitin over the venter of 
the abdomen also is roughened with fine transverse lines. When 
an attempt is made to dislodge a crab by traction on its limbs, an 
additional resistance is often obtained by the elevation of the rostral 
«/ 
region of the carapace against the roof of the chamber. 
The breeding period of E. longicarpus is very long. Females 
with eggs attached to the pleopods can be obtained from May until 
mid-September. The zoeae begin to appear in the auftrieb in the 
latter part of June and are very abundant during July and August. 
The glaueothoe can be obtained as late as October. Our knowl¬ 
edge of the breeding period of the remaining species of Eupagurus 
is imperfect. E. ar.mulipes breeds over practically the same period 
as longicarpus , ceasing a little earlier in the fall. Zoeae that agree 
closely with Sars’ (’89) description of the zoeae of E. bernhardus 
occur scatteringly throughout the summer. Quite likely these are 
the larvae of acadianus. The glaueothoe, however, has eight instead 
of the ten telson bristles shown in Sars’ plate. The young of 
pollicaris have not been identified and most of them are probably 
liberated in June, though females with eggs are taken during July. 
