THOMPSON: METAMORPHOSES OF HERMIT CRAB. 161 
Mxp.i Mxp 3 I 
II III IV V 
0 0 0 0 
0 2 2 2 
0 0 0 0 
0 10 1 
2 2 0 10 
0 0 0 0 
Pleurobranch. 
Arthrobranchs. 
Poclobranchs. 
The larger posterior gills are provided with two short rows of ova 
lamellae, but the smaller anterior ones show at most only two or 
three plates each. The gills on the maxilliped and cheliped seg¬ 
ments are simple and the maxillipedal pair are so minute as to be 
invisible in surface views. They cannot be detected, either, in some 
excellent sections. But since they are very plainly shown in all 
sections of mature glaucothoe and most of the sections in which they 
cannot be seen are of younger specimens, it may be presumed that 
they arise during the period. In this case it scarcely seems possible 
to refer their occasional absence to error in interpretation, although 
such outpushings of the body wall usually appear at and not between 
the ecdyses. Whenever present they are very distinctly shown in 
sections cut in any plane. 
The sixth-stage larva has cheliped gills that are divided into 
two or three lamellae, but its maxillipedal gills are still simple. 
These latter reach a trilamellate condition at about the fortieth 
day from the glaucothoe phase. One crab eighty days from the 
glaucothoe phase showed an anterior maxillipedal gill with four, 
a posterior with twelve pairs of lamellae. 
Internal anatomy .— A brief description of the stomach of the 
adult crab is a necessary preliminary to the description of the con¬ 
struction of this organ in the larvae, but it may be limited in scope 
to an account of the topography. No details of the ossicles are 
necessary, since these cannot be worked out in the serial sections of 
the developmental stages. 
The stomach of the adult (pi. 9, fig. 57) has a cardiac portion of 
more than twice the length of the pyloric. The cardio-pyloric valve 
is crowned with blunt setae. Each lateral tooth consists of two 
rounded tubercles, a comb of transverse rugae, and a hairy terminal 
process. The oesophageal opening is guarded by a pair of upper 
and lower oesophageal plates. The pylorus is broadened laterally 
into a pair of shallow upper, and prominent lower pyloric pouches 
(pi. 9, fig. 57, 52, upp, Ipp). The latter have their inner surfaces 
densely clothed with long setae, and above, the wall of the pylorus 
