BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 18. AFD. IT. N:0 1. 5 



geiietie clevelo])ment among Echinoidea'. Wlien the oesopha- 

 geal end of tlie intestine lias pierced the. membrane that covers 

 the stoma-, and the periproct has been formed in the inter- 

 radium ö, then the post-pluteal stage is finished and its five 

 provisional sncking-feet are no more seen. 



Wyville Thomson relätes of the Goniocidaris canaliculata 

 Al. Ag., dredged at the Falkland Islands^, that its young 

 Avere observed to creep upon the spines of tlie parent by tlie 

 aid of their hve huge provisional suckers. On a specimen of 

 this species. canght at the same oecasion, and for which I am 

 indebted to Mr John Murray, I fonnd a few young ones, the 

 examination of wliieli aifoi-ded the following additional obser- 

 vations. They have l)eeii described and figured long ago by 

 Alexander Agassiz^. 



The young seeni to be all of the same age, tliough sonie 

 are more advanced than others. The diameter, exclusive of the 

 spines, is between 1,4.') mm. and 1,7 mm. The test is consi- 

 derably more depressed tlian that of the ])arent, its height 

 hardly equalling half the diametei'. 



The specimen figured Pl. I, fi(/. 1 may be taken as an 

 example of the least advanced. Its spines are relatively short. 

 The five provisional suckers are verv strong, a(;etabulated, 

 longer tlian the spines and, although contracted, reach consi- 

 derably downwards. There are five pairs of persistent pedi- 

 cels in every ambulacrum. and some tongs. Seen from above 

 the calycinal system of another specimen, Pl. II, fig. o. shows 

 its radials and costals. The radials are lengthened and com- 

 pressed ; at the outer end of each of them the external integu- 

 ment is produced into a provisional sucker, fig. 4, the dm^ts 

 of which communicate witli tlie interiör by means of a pas- 

 sage sheltered by the vaulted adoral margin of the radial. 

 The costals are large, somewliat irregular, each with a small, 

 nearly central spine, and the one of the interradial 2 is per- 

 forated by a large water-pore, ihe precedent of the future 

 madreporite. In the centre there is a small, clear, irregularly 



' Etudes PL XI, fig;. 93—97; PL XXIIL fig. 180, l.Sl ; Pourtalesia p. 70. 

 011 the Ethmophracti among the Spatangid». 



^ Pourtalesia. p. 2G; compare Etudes s. L Echinoidées p. 14. Pl. III. fig. 

 32, ;53. 



' Voyage of the Cliallenger. II, p. 223. 



* Challenger Rep. Echin.. p. 45, Pl. II, fig. 9, 10, l.S. 



