Mr. G. Hodge on the Development of a Species of Pyenogon. 41 
Having traced, with some slight interruptions, the germs to 
the larvee, the larve to the immature and parasitical young, we 
now come to the concluding stages, viz. that period at which 
the young animal, well developed and furnished with the neces- 
sary organs to enable it to provide for itself, seeks an exit from 
the Coryne-sac or vesicle: here the foot-jaws doubtless play a 
most important part. 
Such sacs as contain well-developed animals are found to be 
deeply tinged with colour near the summit : if these are selected 
and kept in clean and cool sea-water, the whole process may be 
watched. The animal evidently uses its foot-jaws to rupture 
the investing skin of the sac, which at this stage, from some 
peculiar circumstance, seems more limp and pliable than at 
other times. An opening having been effected, one or both of 
the claws of the first feet are projected through the opening, and, 
with the usual slow and languid movements of the class, are 
worked about, doubtless widening the breach ; then another leg 
appears, and another, until the whole animal emerges and sprawls 
away. If we examine the figure of the free animal as seen 
shortly after its escape from the sac, it will be noticed that, 
although closely resembling the mature form in those features 
that guide us in the discrimination of the species, it nevertheless 
requires further development. It still has only six legs, the 
fourth pair being represented by short rounded lobes; these 
lobes, gradually growing, become jointed, and are furnished 
with claws and bristles; after which the animal merely requires 
time to mature its several parts. Whether this is gradual, or 
assisted by a further moult, I am not prepared to state: it has 
been seen to perform this process in early life ; so it is not im- 
probable that it may do the same in a more advanced stage*. 
Finally, I figure a male Phoxichilidium coccineum, and also a 
portion of a female, both fully matured; so that the several 
stages, from the germs, devoid of organs of any kind, to the 
perfect animal, may be compared, and their several points of 
difference and gradual growth be fully understood. 
Setting aside for a short space all that has been written on the 
subject of the anatomy of these animals as bearing upon their 
_* Since writing the above, I have been so fortunate as to discover the 
moulted skin of the young Phozichilidium which is cast by the animal 
before or at the time of leaving the sac of the Coryne: this cast-off mem- 
brane is extremely delicate and transparent, and shows the several limbs, 
&c., from which the animal had withdrawn itself, apparently without much 
damage to the exuvie. It therefore seems highly probable that the in- 
crease of growth in these animals is effected in a similar manner to that of 
other Crustacea, viz. by a series of moultings. We have seen two instances 
of this during the embryonic stages, and there is no reason why the process 
should not continue in after-life. 
