Prof. W. Thomson on the " Vitreous " Sjwnges. 127 



hexradiate stellate," and various simple and branched modi- 

 fications of the hexradiate type. 



There seems to be something unusually fatal in the fascina- 

 tions of these beauties. As to Hahrodictyon sjyectosum, it cer- 

 tainly seems almost " useless to continue to quote the singular 

 number of errors into which " every one appears to have " fallen 

 in the description of this beautiful Sponge." Professor Owen, 

 of whom this was first said, has certainly gone least astray, as 

 he has succeeded thoroughly in the object Avhich he had in 

 view at the time, by giving us a description oi Eiqjlectella 

 aspergillum which, if we combine with it that of E. cucumer^ 

 can scarcely be surjDassed. 



1. The use of the name Alcyoncellum by Messrs, Quoy and 

 Gaimard, and the quotation of De Blainville's diagnosis of the 

 genus, is clearly a mistake^ arising from some confusion of the 

 papers on the part of the compilers of this work. " Genre 

 Alcyoncelle [Alcyoyicellum). Corps phytoide, subpierreux, 

 solidifie par des spicules ti'icuspides ; a branches pen nom- 

 breuses, cylindriques ; fistulaire, termine par un orifice arrondi, 

 k parois ^paisses composees de granules reguliers, polygones, 

 alveoliformes, percdes d'un pore a I'exterieur et a I'interieur. 

 Alcyoncellum speciosum^ nob,, pi. 26. fig. 3. Alcyoncellum 

 cylindricum, cavum, extremitate rotundum, album, reticulis la- 

 pidicis elegantissime contextum." The specific description 

 does not in any way correspond ^\\X\\ the diagnosis of the 

 genus. 



2. M. Milne-Edwards ignores altogether De Blainville's de- 

 scription, and refers the generic name Alcyoncellum to Quoy 

 and Gaimard. He adds a fair description of the genus : — 

 " MM. Quoy et Gaimard ont donne le nom Alcyoncelle a un 

 corps qui parait appartenir a la famille des Spongiaires, et qui 

 presente une structure trfes-remarquable ; on peut assigner au 

 genre dont ce zoophyte est le type les caract^res suivans : — 

 Genre Alcyoncelle {Alcyoncellum). Spongiaire lamelleux dont 

 la charpente est form^e de filets tr^s-delies, accoles les uns aux 

 autres, et entrecroisds de mani^re a former des mailles nom- 

 breuses, arrondies, assez reguli^res et semblables a celles d'une 

 dentelle. On ne connait qu'une esp^ce ([^Alcyoncelle^ qui est 

 tr^s-remarquable par sa beaute et qui a ete rapportee des 

 Molluques par MM. Quoy et Gaimard, elle a la forme d'un 

 panier profond et ^troit dont les parois seraient composees d'un 

 tissu delicat d'un travail analogue a celui des sidges a rotang 

 dont les modules nous viennent de I'lnde. Ces naturalistes lui 

 ont donne le nom de Alcyoncelle specieux (Quoy et Gaimard, 

 Voyage de 1' Astrolabe)." 



10* 



