Dr. F. Miller on the Metamorphoses of the Prawns. 111 
bristles, especially the apex of the longer external lamina; the 
long plumose setz of a later period are still wanting. By the 
sprouting forth of the caudal appendages on the ventral surface, 
* our animals are distinguished not only from the Porcellane, but 
also from those Prawns which quit the egg in the Zoéa-form, 
and in which, as in Porcedlana, these lateral caudal lamin are 
produced within the broad caudal fin. 
The gradual changes which the appearance of the animal 
undergoes in consequence of the development of the paired eyes 
and the new body-segments and their appendages, are followed, 
when it has attained a length of about 1°6 mill., by a new 
fundamental and sudden metamorphosis—the change into the 
Mysis-form (fig. 8). The antenne cease to serve for locomo- 
tion; they are replaced by the setigerous thoracic feet and by 
the long abdomen, which, having been hitherto painfully 
dragged along like a useless burden, now, by means of its power- 
ful muscles, impels the animal rapidly with a jerking move- 
ment. 
The carapace, with its frontal process still undenticulated, has 
acquired two short teeth on each side of its anterior margin— 
one over the eye, the other on the inferior angle. It soon en- 
tirely covers the thoracic segments, of which some at first re- 
main uncovered, at least above. 
The anterior antenne have lost their long sete. The first 
three joints now appear as a peduncle, a second branch, at first 
unjointed and running out into a simple seta, being developed 
inwards from the fourth bacilligerous joint. 
The exterior branch of the posterior antenne has become con- 
verted into the scale of the antenna of the Prawn, namely, into 
an unjointed leaf, the outer margin of which is furnished with a 
short tooth, whilst the more prominent apex and the inner 
margin are fringed with long plumose sete. Close to this la- 
mina, within and below it, there is a short, bristleless, unjointed 
lobe, from which the flagellum of the antenna is subsequently 
produced (figs. 811, 9). Whether this lobe is developed from the 
inner branch of the antenna of the Zoéa, or whether it is a new 
formation, whilst that inner branch entirely disappears, I must 
leave undecided: the latter appears to me most probable; and 
I think that the flagellum of the Prawn’s antenna is to be re- 
garded as the median branch (palpe, M.-Edw.). 
The feet already existing in the Zoéa have undergone no parti- 
cular change. The third pair of footjaws now resembles the two 
preceding ones. The five new pairs of feet are at first all of 
the same structure; the unjointed peduncle bears a short and 
likewise nnjointed inner branch with two terminal sete, and an 
outer branch, of twice the length of the other, annulated in its 
