OF CRUSTACEA. 



371 



Double Metamorphosis in Macropodia Phalangium. 



This, which is our common spider-crab, is very abundant in 

 the deep water of the harbour of Cove, and is often met with 

 in spawn during the summer months ; but as these kind of 

 crabs are not to be kept alive out of their proper element, it 

 was only by chance that I succeeded in discovering its larva, by 

 capturing a female on the very point of hatching. This not only 

 enabled me to sketch its imperfectly developed larva, (fig. 1,) 



Fig. 1. 



but also to secure a stock of them, as the best proofs of a fact 

 which many zoologists are yet inclined to disbelieve. These 

 sufficiently show that the larva is a Zo'e, with only two pair of 

 cleft members. Megalopce, of the same yellowish brown 

 colour as the spider-crab, are also not uncommon in the 

 same locality, but the full grown Meyalopa (fig. 2.) has 

 so much of the character of the perfect crab in its colour, 

 texture, antennae, and spines of the corselet, as to render it 

 almost certain that it belongs to no other species ; taking into 

 account the discoveries previously made of double metamor- 

 phosis, and that the Brachyura pass through this intermediate 

 disguise in quitting that of Zo'ea. 



In this instance, the proof is certainly not quite so clear and 

 satisfactory as in those above referred to, and although the 

 probability is in favour of the opinion I venture to hazard, yet 

 it might be the Megalopa of the M. Dorsettmsis, the only 

 other species common here, to which it could possibly belong. 



