Capt. DuCane on the Metamorphoses of Crustacea. 439 



I beg to trouble you with the following particulars and ac- 

 companying drawings of this animal, which I believe has not 

 hitherto been figured, and is otherwise interesting, as con- 

 firmatory of the fact of some species of the Brachyurous, as 

 well as the Macrourous Decapods, being subject to a succession 

 of changes before they reach theh adult state. 



The crabs from which this larva was obtained were brought 

 to me carrying their ova under their abdomen as early as the 

 latter end of December last, but it was the beginning of 

 March before one of them began to produce its larvae, and 

 even then, and indeed during the whole of the month of March 

 and great part of April, comparatively few of the ova were 

 hatched. The form of the larva up to this period is shown in 

 fig. 1.; it exhibited no other symptoms of life than merely 

 slight movements of the limbs and antennae, and although fully 

 developed, was fi:*om this circumstance, and the extreme trans- 

 parency of its different organs, exceedingly difficult to deli- 

 neate. Towards the end of April however, after the crabs had 

 been carrying their ova for a period of four months, I had 

 the satisfaction to find the larvae alive in great abundance, a 

 large mass lying at the bottom of the vessel in which the 

 crabs were kept, still of the same form I had found them pre- 

 viously, but vast numbers of others swimming about the surface 

 of the water of the form shown in Plate XI. fig. 2. 



I was much surprised at thus finding myself suddenly in 

 possession of apparently two different animals ; but the fact is, 

 as I soon discovered, the larva is scarcely excluded from the 

 egg of the form PI. XI. fig. 1., before it casts off this enve- 

 lope, and assumes the appearance represented by PI. XI. 

 fig. 2. ; indeed the animal, as it appears in this latter state, is 

 distinctly visible through the delicate and highly transparent 

 envelope which incloses it in its first condition, as I have en- 

 deavoured to show" both in fig. 1. and in the equally highly 

 magnified sketches of the tails, figs. 5 and 6. 



As the ova continued to be hatched in great abundance du- 

 ring many successive days, I had repeated opportunities of ob- 

 serving this change effected ; it is accomplished as follows : — 

 On its first liberation from the egg, the larva lies on its side, 

 and seems to be only capable of progressing through the water 



