222 Mr Thompson cm the Metamorphoses In the 



zoea than in its members, which are similarly cleft, with the 

 outer divisions adapted to natation. Slabber (as suggested 

 Zool. Res. p. 8), no doubt committed some serious mistake ; for, 

 making allowance for the greater accuracy of the delineations I 

 have given, there is every reason to suppose the two animals 

 identical, or that both are derived from the same individual spe- 

 cies of PalcBmon^ viz. serratus. 



As it would be highly desirable to trace the metamorphoses 

 of these larvae into the perfect animal, it was attempted to pre- 

 serve them alive, but without success. 



At the same season of the preceding year, an animal was cap- 

 tured, (of which Fig. 2. is a representation), the correspondence 

 of which with the above larvas, in colour and size, renders it 

 more than probable that it is the same in a more advanced stage, 

 having acquired an additional pair of cleft members, and a pair 

 of scales at each side of the tail, as in the animal figured Zool. 

 Res. pi. i. fig. 6. a, from the equatorial region of the Atlantic, 

 which we may therefore consider as the advanced larva of some 

 oceanic type of this tribe. 



Another animal, which can be no other than the prawn in a 

 still more advanced stage, was taken July 25. 1824, (Figs. 3, 

 4, 5) : in this remarkable stage, it is now no longer doubtful to 

 what perfect type it belongs, as it presents the general appear- 

 ance of the prawn, but still retains the natatory division of the 

 members, now increased to six pair ; the subabdominal fins, al- 

 though conspicuous, are as yet rude ; and the frontal spine or 

 rostrum exhibits only three serratures, placed far behind, over 

 the dorsum of the corselet. Still it is so remarkably prolonged 

 in front, as nearly to equal the antennae in length. 



We have here three distinct stages, in each of which the ani- 

 mal differs considerably ; and from the disparity in size between 

 the second and third, it is most probable that there is at least 

 one intermediate stage between these two, in which the larva 

 may be supposed to present a shorter rostrum than the last, with 

 fewer or no serratures, and a less number of cleft members* 

 This being kept in view, will prevent such observers as may 

 meet with animals of this description from unnecessarily bur- 

 thening the class with new genera and species. Indeed it must 

 be deemed a fortunate circumstance on this account, that the 



