142 DEVELOPMENT OF PALINURUS VULGAEIS. 



situated behind the mouth. The second part of the body was the 

 thorax, quite as fiat but not so large as the head ; it was usually 

 broader than long. It presented no trace of a division into seg- 

 ments, but on its lateral edges carried four to six pairs of long, 

 delicate, articulated limbs, each of which was provided with a 

 secondary shorter branch fringed with hairs on each side. The 

 disposition of the abdomen varied ; in some species it was distinctly 

 marked off from the thorax and much narrower, sometimes situated 

 in an emargination of the posterior edge of the thorax, and some- 

 times again it was at its base as broad as the thorax, of which it 

 formed a direct continuation. Usually six or seven segments were 

 visible in the abdomen, the last of which bore biramous flat appen- 

 dages, like those of the lobster, on each side of the telson. Accord- 

 ing to these differences in the abdomen, Milne Edwards divided the 

 species of Phyllosoma into three groups : (1) those which had a 

 distinct well-developed abdomen, narrower than the thorax, Phyllo- 

 somes ordinaires ; (2) those in which the abdomen was rudimentary, 

 and situated in an emargination of the thorax, PJiyllosomes hrevir 

 caudes ; (3) those in which the abdomen was broad and continuous 

 with the thorax, Phyllosomes laticaudes. 



Since the date of Milne Edwards' work, various more or less in- 

 complete researches have proved that the forms belong-ing to the 

 genus Phyllosoma, as defined by the characteristics just described, 

 are the early stages or larvae of Palinurus and its allies, that is, of 

 the Decapod Crustaceans of the family Palinuridse or Loricata. 

 Balfour, in his Comp. Embryology, vol. i, p. 477, states that the true 

 nature of Phyllosoma v^&s first shown by R. Q. Couch in a paper on 

 The Metamorphosis of Decapod Crustacea in the Report of the 

 Cornwall Polytechnic Society of 1848, but that Couch did not recog- 

 nise the identity of his larva with Phyllosoma, which was first done 

 by Gerstacker. This statement is incorrect, probably because 

 Balfour was unable to refer directly to the Reports of the Cornwall 

 Polytechnic Society, to which I have access in the library of the 

 Plymouth Institution. R. Q. Couch's first paper on The Metamor- 

 phosis of Decapod Crustaceans is in the Report of the said Society 

 for 1843. The description of the newly hatched Palinurus there 

 given is quite erroneous. Couch states that he obtained gravid 

 specimens of Palinurus from the fishermen, and kept them in crab- 

 pots until the eggs hatched. His description of the hatched larva 

 is as follows : — " The whole animal is smaller and more slender than 

 the young of the lobster. The body is oval, slightly depressed ; 

 eyes rather small compared with other species, sessile, marked at 

 its circumference with radiating lines, and situated on a festoon of 

 the dorsal shield, The claws are in four pairs, similar to those of 



