268 4H. Rathke on the Metamorphosis of the Crustacea. 
nearly as thick as broad. At its extremity there was a large 
irregular triangular plate, which had at its posterior broad 
margin, or base, a moderately deep but long incisure, and at 
whose two posteriorly directed corners two long, thick spines 
directed backwards were inserted (articulated). False legs 
were already present, not yet divided into two branches, 
but nearly cylindrical. Two simple appendages, like the false 
feet, but of smaller size, were inserted on both sides of the 
lamina, representing the fan, at (into) the hinder extremity of 
the sixth joint of the tail. 
Together with the above-described larvee were likewise 
captured some others which had swum deeper. Now these 
were very much further developed, and already possessed a 
considerable resemblance to full-grown specimens of Hyas 
Araneus : for instance, the antenne, foot-jaws and legs were of 
similar form and relative dimensions as in these ; this was like- 
wise the case with respect to the dorsal shield, only that this 
shield terminated in front in three rather long, thick spines, 
lying nearly in one and the same horizontal plane, of which 
the central one was larger than the two others. The tail, on 
the contrary, was proportionately much longer than in full- 
grown specimens, and was likewise of a moderate breadth and 
pretty thick. The false feet were very long in comparison to 
the tail, and were already provided with two branches unequal 
in size, and furnished with very long bristles. The fan con- 
sisted of a broad, moderately long, and posteriorly rounded 
plate, and of two minute and simple longish-oval lamine, 
likewise inserted on both its sides at the sixth joint of the tail ; 
these laminz were only about half as long as the false feet of 
the fifth joint of the tail. 
From the notices which I have here briefly communicated 
respecting the development of some Decapods, it therefore 
results that several of these animals, as first discovered and 
described by Thompson, undergo a very considerable and 
highly remarkable metamorphosis, after having thrown off 
their egg-shells. I therefore confess that I have done Thomp- 
son injustice in not putting faith in that discovery, relying on 
the history of the development of the Cray-fish, and trusting 
too much to analogies in the structure of full-grown Decapods ; 
perhaps likewise led into error by the examination of very 
small embryos of Eriphia spinifrons and of Palemon Squilla. 
It results, however, from the above communication, and 
from the history which I have given of the Cray-fish (and 
which I intend next spring partially to subject to a revision), 
that different Decapods quit their eggs in a different stage of 
