THOMPSON: METAMORPHOSES OE HERMIT CRAB. 201 
this genus have these scales in the glaucothoe stage. As the figure 
was drawn from a specimen collected near Woods Hole, a region 
•characterized by the practically exclusive predominance of the genus 
Eupagurus this would be a most unlikely contingency. 
At the present time three u species” of Glaucothoe are recognized, 
but Bouvier ('91) has noted that the specimens of G. peronii 
collected by the “ Talisman ” are not wholly like Milne-Edwards’ 
type specimen. If as I believe, the glaucothoe phase in the crabs 
from which these larvae are derived, is short and without any appre¬ 
ciable growth, these discrepancies can no longer be explained as 
differences in age and development. They indicate rather that the 
young of more than one species of hermit crab have been grouped 
under the single name. 
Summary. 
The adult Eupagurus has a dextral asymmetry which not only 
affects every organ in the abdomen but extends into the thoracic 
region, so that scarcely any system of organs in the body escapes 
some modification or displacement. However, with the exception 
of the flexor muscles and arteries of the abdomen, the homologies 
with corresponding parts in other Decapoda are clear. But the 
diagonal muscle bands and the peculiar division of the superior 
abdominal artery into the two trunks, b and b\ are interpretable only 
from a study of the larva. The muscles are then shown to be a 
greatly degenerated loop-enveloping system from which the trails- 
versalis muscle has been lost. The arteries resolve themselves into 
supra-abdominal and a new vessel, primarily derived from the second 
segmental artery of the right side. This latter artery is probably 
peculiar to the Pagurids and without homologue among the higher 
Macrura. 
The development is concentrated. There are four stages in the 
zoea phase, the last of which is a metazoea. The postzoeal or glau¬ 
cothoe phase consists of one stage which is Macruran in general 
form and from the first presents a mingling of adult and larval char¬ 
acters. The external anatomy, especially of the cephalothoracic 
region, recalls the adult. The appendages — except the pleopods 
—the gill formula, the asymmetry of the chelipeds and uropods, 
•the structure of the stomach, the concentration of the nerve ganglia 
