134 On the Development of some Pelagic Decapods. [Dec. 16, 



mode of development is very simple. After the first moulting the larva 

 gets six more branched legs and loses many spines. It enters the 

 Amphion stage, then moults, throws the branched legs off, gets branchial, 

 and becomes a young Sergestes. Only after this last moulting the central 

 eye, hitherto present, disappears. 



And very similar to that of Sergestes is the development of Leucifer. 

 Here the earliest Zoea of a species from the Western Pacific has got at 

 first no eyes, then sessile ones come out, and the animal then presents 

 the form which Dana has called Erichthina demissa, and which Claus 

 suspected to be not a Stomatopod but a Schizopod larva. After the 

 second moulting this Erichihina gets stalked eyes and very long setae on 

 all its appendages, becoming a rather long, very delicate Zoea. It now 

 enters the Amphion stage, but never gets more than four pairs of pereio- 

 pods, and loses another pair of these when it moults for the youngest 

 Leucifer stage, in which two pairs of pereiopods are absent. 



The next question, after having found this out, was, of course, whether 

 Amphion, Sergestes, and Leucifer leave the egg as a Zoea, or whether 

 there is a preceding Nauplius stage. My own impression is that in the* 

 two first-named genera this is not the case, as the youngest Zoeas which 

 I caught had all the same size, and as none of them was without the 

 large lateral stalked eyes. As for Leucifer, the question appears to me 

 to be doubtful ; for it is, from what I have seen, quite possible that my 

 youngest Zoea, which has only got a central eye, may be preceded by a 

 Nauplius. Of course the simplest thing would be to get the eggs ; but 

 there is the difficulty, for Amphion is caught very rarely, and has never 

 been obtained at any other time but between 8 and 12 p.m., when it is 

 extremely difficult by lamplight to find out the youngest stages. Sergestes 

 larvae are commoner, appearing also in the daytime, and Leucifer is 

 sometimes caught in abundance. I hope, therefore, that I shall succeed 

 in completing my researches about this question, especially as far as the 

 two latter genera are concerned. 



H.M.S. ' Challenger,' Honolulu, Sandwich Islands, 

 July 30, 1875. 



December 16, 1875. 



Dr. J. D ALTON HOOKER, C.B., President, in the Chair. 



The Presents received were laid on the table, and thanks ordered for 

 them. 



The following Papers were read : — 



