Dr. F. Miiller on the Metamorphoses of the Prawns. 1 1 i 



bristles, especially the apex of the longer external lamina ; the 

 long plumose 8et« 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 Porcellana, but 

 also from those Prawns which quit the egg in the Zoea-form, 

 and in which, as in Porcellana, these lateral caudal laminae 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-(orm (fig. 8). The antennte 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 undent iculated, 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 anteruut have lost their long setae. 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 antenna 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 sets. Close to this la- 

 mina, within and below it, there is a short, britttleless, unjointed 

 lobe, from which the flagellum of the antenna is subsequently 

 produced (figs. 8 ii, 9). Whether this lobe is developed from the 

 inner branch of the antenna of the Zoea, or whether it is a new 

 formation, whilst that inner branch entirely disappears, I must 

 leave undecided : the latter api>ear8 to me most probable ; and 

 I think that the flagrllum of the Prawn's antenna is to be re- 

 garded as the median branch {palpe, M.-Edw.). 



The feet already existing in the 2^€a 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 unjointed inner branch with two terminal setae, and an 

 outer branch, of twice the length of the other, annulated in its 



