OP METAMORPHOSES IN THE CRUSTACEA. 325 



first and second pairs of foot-jaws of the typical Decapods immensely developed ; the 

 minute pair of organs following these to be the third pair of foot-jaws ; the five pairs 

 of " limbs of the future Crab" to be the real thoracic legs of the Zoe, and that the 

 minute fleshy masses are evidently branchiae. Thus we perceive that the possession 

 of these limbs, instead of being an evidence of the imperfect state of the Zoe, is a 

 proof of its anomalous perfection ; and thus we arrive at the unexpected conclusion 

 that Zoea is a genus of Decapod Crustacea, for the reception of which amongst the 

 Macroura a distinct section must be established. 



With reference to Mr. Thompson's statements respecting the hatching of the Zoes 

 from the eggs of the common Crab, and the arguments adduced from the habits of 

 the West Indian land Crabs, I am able to offer the following as, I trust, very conclu- 

 sive observations to the contrary. 



In the collection above alluded to were contained, in spirits, the abdomens of seve- 

 ral female Crabs, having the interior surface covered with hundreds of eggs or newly 

 hatched young. One of the bottles in which one of these was deposited was labelled 

 by Mr. Guilding, " Eggs and young of a land Crab not undergoing a metamorpho- 

 sis." From this specimen I obtained eggs, and young Crabs evidently just hatched, 

 and others at a rather later stage of their growth. 



The eggs are of a dark reddish colour, showing through the outer integument the 

 rudimental limbs of a future animal of a paler colour. On removing the thin trans- 

 parent pellicle which surrounded one of these eggs, the eyes of the future animal were 

 most conspicuous, the tail was seen extended as a narrow plate, nearly reaching to 

 the eyes, and along its sides lay the large anterior cheliferous and the four following 

 simple pairs of limbs. The existing organs, although perfectly discernible, occupied 

 only a small portion of one side of the Q^g, its greater part being filled with hardened 

 matter composed of minute molecular grains. The animal was in a sufficiently for- 

 ward state of development not to allow the least doubt to be entertained as to the 

 nature of these limbs, nor did any organs appear answering to the two large split 

 pairs of natatory organs of Zoea. The branchiae, in a fleshy and unorganized state, 

 were also found at the base of the legs. The eggs are \\ line in diameter. 



In the accompanying sketches I have represented one of the Crabs evidently just 

 batched, being about If line long, and having the upper part of the cephalothorax 

 considerably swollen. From my figures, the very rudimental state of the two pairs of 

 antennae, and of the feelers or flagrums of the outer foot-jaws, will be perceived ; but 

 the general form of the animal is thus early exhibited, and the developed state of its 

 branchiae and the want of subabdominal appendages are especially noticeable. In 

 the following sketch the animal is seen in a somewhat more advanced stage of its 

 growth, being rather more than 2 lines long, and in which the upper surface of the 

 cephalothorax has acquired its ordinary shape, and the antennae have attained a 

 greater degree of perfection. 



