METAMORPHOSES OF THE CRUSTACEANS. 261 
movable style like a sword. One species, L. Polyphemus, is often found 
near our coasts; and we have frequently seen numerous specimens, after a 
storm, strewn lifeless along our shores. It is from one to two feet in 
length. 
As the other orders of this class contain nothing of peculiar interest, we 
close our observations on the Crustaceans with a few general remarks. 
The facility with which the Crustacea cast off their legs, and even their 
heavy claws, when they have been wounded in one of these organs, or 
alarmed at thunder, is most remarkable. Without the least appearance 
After 
a time a new limb crows out of the old stump, but never attains the size 
of the original limb. 
The wonderful metamorphoses of the insects are universally known, but 
of pain, they then continue to run along upon their remaining legs. 
the changes which the young crabs have to undergo ere they assume their 
definitive form are no less astonishing. We are indebted to Mr. Vaughan 
Thompson for the first discovery of the metamorphoses of the Common 
Crab; and since then the evolutions of many other Crustaceans have been 
observed by other naturalists, so that most likely all the more perfect Crus- 
taceans undergo analogous changes. 
Before Mr. Thompson’s observations, the small creatures, which he proved 
to be young crabs, were considered as belonging to a distinct genus, called 
Zoea. “On creeping out of the ege, these larve look very strange indeed. 
Fancy a preposterously large helmet-shaped head, ending behind in a long 
point, and furnished in front with two monstrous sessile eyes, like the win- 
dows of a lantern. By means of a long, articulated tail, the restless chi- 
mera continually turns, so to speak, ‘head over heels.’ Claws are wanting ; 
while the old crabs have eight legs, the young have only four, armed at the 
extremity with four long bristles, that are continually pushing food towards 
the ciliated and ever active mouth. Who could imagine that a creature like 
this should ever change into a crab, with which it has not the least resem- 
blance? But time does wonders. Immediately after the first casting of the 
skin, the body makes an approach to its future permanent form; the eyes 
are raised on stalks ; the claws and feet begin to develop themselves ; but as 
yet the metamorphosis is incomplete, for the tail remains long, like that of 
the lobster, and is used by the young crab to swim about merrily in the 
water. It is not before the next stage, when the little creature measures 
about one eighth of an inch in diameter, that the crab form is complete- 
ly developed by the tail shortening, and finally disappearing under the 
shield. 
“In these successive metamorphoses, we 
stages of formation. In the first, the crab 
NO. XVII. 86 
see the peculiarities of several 
is like one of the lowest and 
