THOMPSON: METAMORPHOSES OF HERMIT CRAB. 
191 
In the summer of 1900, a number of crabs from “sinistral” 
experiments were kept with sinistral shells. No especial attention 
was paid them. One of these grew much more rapidly than its 
mates and when it was about eighty days past the glaucotlioe phase 
it was examined. It then had a carapace 3.7 mm. in length, an 
antennal flagellum of 35 joints, an ophthalmic scale which w r as adult 
in form, and sexual “pseudo-orifices ” on the third pair of limbs, i. e., 
in the female position. The pleopods, however, were of male number 
and type with the addition on the right side of the fourth segment 
of a pleopod exactly like the corresponding appendage on the left. 
The formula was : O, R, R, R,: O, O, R, O. 
I am not inclined to attach much importance to this peculiar 
specimen and least of all to regard its peculiarities as connected with 
its life in a sinistral shell. With the exception of the pleopod 
it was internally and externally, a dextrally asymmetrical crab. 
Although it had lived for eighty days from the glaucotlioe, it had 
not lost the male type of pleopod, when normally the female type 
should be almost or completely established. Moreover, the pleo¬ 
pods were of male number, while the “ pseudo-orifices ” were in the 
female position. It seems to me that this crab was merely a sport, 
resulting very probably from the unnatural conditions of captivity, 
and just as likely to have appeared in one series of experiments as 
in another. However, it certainly shows that the retained rudiments 
of the sixth stage may occasionally be conserved or reconstructed. 
An attempt, during the following year, to repeat this experiment 
w T ith larvae that were known to be variants, was unfortunately 
rendered inconclusive by an unusually high mortality. One hundred 
and eighteen variant sixth-stage crabs were collected, chiefly from 
“ naked ” and “ sinistral ” experiments, and reared to the adult form 
under the following conditions : 30 in dextral shells, 7 in straight 
tubes, 30 in sinistral shells, and 58 without shells. Out of 
these only 37 survived to be examined—a dead crab is almost 
immediately so mangled by the survivors as to be worthless for 
study — and in no case did any crab preserve the variations beyond 
the seventh stage and only 16 percent retained them into that stage. 
That is, whenever the moult from the sixth stage failed to give the 
normal adult pleopod formula, the succeeding ecdvsis produced it. 
Further investigations ought to be made in this direction. They 
require but little care outside of a supply of food, as metazoea may 
