476 ROBERT GURNEY. 



In fact, it must Le confessed that the most striking feature 

 of the z o a)a of Corystes, namely, the great length of the spine, 

 recalls the zoa3as of such Oxystomata asDorippe andEthusa 

 —forms from which it differs essentially in other respects — 

 more than those of the Portunidfe. 



Still the final stages of the metamorphosis show that the 

 peculiar emarginate rostrnm of the adult (which recalls that 

 of the Oxystomata) is preceded by a three-toothed rostral 

 prominence which exactly resembles that found in most 

 Portunids. That the central tooth represents more than a 

 mere entogenetic stage in the reduction of the long rostral 

 spine of the larva is also confirmed by the retention of a 

 trifid rostrum in the adult of Pseudocorystes and Trachycar- 

 cinus (Faxon). 



The existence of this Portunid stage in the development of 

 Corystes was, I understand, the subject of a verbal comnnini- 

 cation made by Mr. Garstang to the Toronto meeting of the 

 British Association in 1897 under the title " On Recapitula- 

 tion in Development, as illustrated in the Life-history of the 

 Masked Crab (Corystes)." As Mr. Garstang has been unable 

 hitherto to write np his observations for publication, and as 

 he informs me that the material at my disposal is more 

 complete than in his own case, I am glad to be able to give a 

 full account of the metamorphosis, and to confirm his obser- 

 vations. I may here express my indebtedness to him for his 

 kind advice and many suggestions during the carrying out of 

 my work. 



Plymouth; M<uj, 1902. 



BlIiI,10(iRAriIY. 



Cano, G. — "Sviluppo posteiiihryoiialo dei ])oiii)piilci, Leucosiadi, Corys- 

 toidei, c Grapsoidi," Napoli, 'Alii dclla R. Accad. d. Sci. risichc c 

 Matem.,' 1891. 



Claus, C. — ' Uiitcrsiiclmiigeii zur Eiforsclumi^ der gcncalogisclicii Grund- 

 lagc dcs Ciustaceensystems,' Wicn, 1876. 



