148 COUCH ON PHYLLOSOMA COMMUNE OF CORNWALL. 



the globe of the eye and a small part of the stalk supporting it 

 being of a rich brown ; but those who saw the animal alive informed 

 me, that on the sides of the carapace were patches of the colour of 

 silver, which, however, had vanished when it came to my hands. 



At first nothing could be discerned of its interior organization, 

 beyond some slight lines, which appeared to be nerves or blood- 

 vessels, and which proceeded from the upper border of the thorax 

 to the antennae or eyes. But as the glycerine penetrated into its 

 substance, the structure became visible without being obscure. 

 Proceeding from the narrow longitudinal line, the whole breadth 

 of the carapace presented an organization which I could not doubt 

 was branchial. The organ on either side appeared to arise with 

 11 roots : the shortest, which were in front, were simple ; but the 

 greater number were bifurcate, and some had no less than four 

 divisions, 22 in all. The four pairs of legs are inserted into the 

 border of the thorax, and at the place of insertion the margin 

 appears to possess a little angularity, and lines of greater density 

 are seen passing off from the coxae towards a place of meeting in 

 the middle. Those I suppose to be muscles. 



[Memoeandum.] 



The species of Fhyllosoma represented in the figure accom- 

 panying Mr. Couch's paper, appears to differ in one respect from 

 the form described by M. Edwards under that name, in which the 

 cephalic tergal plate is stated to be less than the thoracic. The 

 diversity, however, may be due to difference of age or sex ; and it 

 is to be remarked, that Mr. Couch's figure corresponds very closely 

 in this and other respects with that of Phyllosoma coonmtme 

 (Leach) given in Tuckey's * Voyage to the Eiver Zaire,' p. 417, 

 PI. 18. fig. 6. 



The very recent researches of Dr. Gegenbaur (Siebold and Kol- 

 liker's Zeitsch. f. "Wiss. Zoolog. Band v. p. 352 ; and Miiller's 

 Archiv, 1858, p. 43) have thrown much light upon the internal 

 organization of JPhyllosoma. Yvovn these it would appear to be 

 placed beyond doubt, that the organs supposed by Mr. Couch to 

 be internal hrancJiice, are in reality, as suggested by M. M. Edwards 

 (Hist. Nat. des Crustacees, t. ii. p. 475), the liver, and that the 

 respiratory function is performed chiefly by the expanded external 

 surface of the body, although special organs analogous to branchiae 

 exist in the form of feathered appendages to the feet. 



Eor the detailed information concerning the nervous, circulatory 

 and alimentary systems in Vhyllosoma^ reference should be made 



