298 I. IJIMA : HEXACTINELLIDA. I. 



Contents. 



Page. 



Introiluctiiin 1 



Topcigraiihy of tlie Sagarai Sea. (PI. XIV) 6 



Collecting Hexactinelliila and other deep-sea animals in the Sagatui Sea lt> 



Methods used in the studies S'Z 



EUPLECTELLIDJE. 



Eupleddla Owes 37 



Key to the species of Euplecle/la 58 



Euplectella imperialis Ij. (Pis. I & II) 59 



General cliaracters (iU 



Spiculatlon 69 



Young specimens 70 



IMiscellaneous notes. (Affinity of the species. Regeneration. Commensal immates) ... 83 



Euplectella marshalli Ij. (Pis. Ill, IV & V) 86 



General charactei-s 88 



Spiculatiou 96 



Young specimens 103 



Soft Parts IK! 



General arrangement of the soft parts and their relation to the spicules ... 117 



The flagellated chamber 128 



The trabecular 147 



Cells in connection with trabecuhe 165 



Archaiocytes 165 



Thesocytes 173 



Reproductive elements IT'.i 



Summaries of live hiUuloyy of E. marsluilli I'JO 



Development of hcxasters 102 



IMiscelUineons notes. (Affinity. Regeneration. Connaensal inmates) 200 



Euplectella oweni IIekkl. >^ M.vksh. (PI. VI) .. 202 



General cliaracters 204 



Spiculatiou 211 



Miscellaneous notes. (.Abnormal sicvc-plate. Conunensal inmate, &c.) 21.') 



Euplectella curvistellata n. sp 217 



R-ijadrella O. Scn.M 220 



Regadrella okinoseana IJ. (Pis. Vll c*i VIIM 223 



General characters 224 



Spiculation 220 



Young specimens 239 



Soft parts 247 



MisLcllanei'\i> XoU'>. (Kelalion toA'. deconi. Malformations.) 248 



Regadrella komeyamai Ij- (Pis. IX & X) 252 



General cliaracters 252 



Spiculation 258 



