THOMPSON: METAMORPHOSES OF HERMIT CRAB. 
169 
Sex is recognizable at the seventh stage, from six to twelve days 
after the close of the glaucothoe phase, when the males lose the 
rudimentary pleopod on the second segment (pi. 4, fig. 6, ru). But 
the secondary sexual characters in the female pleopods (pi. 6, fig. 24) 
do not begin to appear until thirty or forty days of adolescent life 
have passed and then their development is quite gradual. 
This early differentiation of sex in Eupagurus longicarpus and 
tmnulipes has an interesting bearing on the subject of parasitic 
castration as it exists in the allied JEupagurus bernharclus. There, 
Giard (’86) has found that the male crabs if infested with a Bopyrid, 
Athelgespaguri, have pleopods of female number and form; while 
the females w^hen parasitized with the Cirriped, Peltogaster, bear 
the typical female number of appendages, but in type these approxi¬ 
mate those of the normal male. No data is at hand with respect to 
the adolescent development of JE. bernharclus , but if it resembles 
that of our species at all closely, the modifications shown by the 
parasitized males require either the attachment of the parasite very 
early in adolescent life, or a sufficiently potent effect from its presence 
to cause a reappearance of the pleopod on the second segment. The 
alterations of the parasitized females on the other hand, would be 
explainable as arrest of development. The parasite presumably 
might attach itself at any time within the first fifty days of adoles¬ 
cent life and yet be able to check the complete development of the 
female type of appendage. No ecto-parasite has been found on our 
Eupagurus anniclipes. The only ecto-parasite on E. longicarpus , a 
Bopyrid, Stegophrgxus hyptius , produces no alteration in the second¬ 
ary sexual characters of the host. 
The circulatory systems of our various species of Eupagurus are 
similar in all, and that of E. bernharclus (Bouvier, ’ 91 ) will serve as 
the type. The hepatic arteries are wholly thoracic, so that only a 
.small part of the liver receives blood from this source. The ven¬ 
tral thoracic artery terminates posteriorly with the branches to the 
fifth pair of limbs and the abdomen is supplied by the superior 
abdominal alone. As this artery enters the second segment of the 
abdomen, it divides into two trunks : b and b'. The former is a 
small vessel which courses superficially to the left, supplying livers, 
sexual glands, and appendages. The latter is a larger trunk which 
plunges downward to the right of the intestine, runs caudad along 
the dorsal surface of the flexor muscles, and then in the fourth seg- 
