128 Prof. W. Thomson on the “Vitreous” Sponges. 
3. Professor Owen recognizes, apparently from the figure in 
the ‘ Voyage de l’Astrolabe,’ the generic distinctness of Habro- 
dictyon from Euplectella. He gets into confusion, however, 
about the synonymy. “If the basal aperture of the cone were 
open, the resemblance to some of the known reticulate Aleyo- 
noid Sponges would be very close, especially to that called 
Alcyonellum gelatinosum by M. de Blainville (Alcyonellum 
speciosum, Quoy & Gaimard); its closure by the reticulate, 
convex frilled cap in the present instance establishes the ge- 
neric distinction.” 
4, Dr. Bowerbank’s references and remarks are curiously 
inaccurate: Dr. Gray has, however, already done them full 
justice at the close of a short paper in the ‘ Annals’ for 1866, 
except in one point. Dr. Bowerbank’s definition of the genus 
Alcyoncellum is utterly inapplicable to the Sponge which he 
adopts as a type! and, in the simple process of adopting it as 
such, he contrives either to misname the Sponge or to mis- 
quote the authority. 
5. Dr. Gray does not succeed in throwing much light upon 
the question ; for, still under the fatal spell, he notices Huplec- 
tella aspergillum under the name of L. speciosa, and says :— 
“'This Sponge was first described and figured, in 1833, by 
MM. Quoy and Gaimard, in the ‘ Voyage of the Astrolabe,’ 
p- 302, Zoophytes, t. 26. f. 3, under the name of Aleyoncellum | 
speciosum, from a very imperfect specimen which had lost the 
netted lid, the fringes on the outside, and a considerable por- 
tion of the smaller, lower end of the tubes.”” * * * “ There can 
be no doubt of the imperfect state of this Sponge, from a com- 
rae with a worn and crushed specimen in the British 
useum, that was obtained by Capt. ir Edward Belcher, and 
purchased at the sale of his shells.’ 
6&7. Dr. Gray has at length fully recognized Huplectella 
and the species in the French Museum as belonging to distinct 
genera; nay, he has founded two new genera upon the speci- 
mens in the Jardin des Plantes. I certainly suggested to Dr. 
Gray, in May last, in a letter which he has quoted (op. cit.), 
to iskiee a new genus for the French forms; but I cannot 
ossibly consent to the splitting of that genus. Genera are 
Tiecttidles of the highest convenience if they represent groups 
of nearly allied species; but to give a generic name to almost 
every species, entirely does away with the value of the genera, 
and, instead of assisting the student, only adds to his per- 
era 5 For a time I doubted whether these two forms 
were distinct species ; and I was inclined to regard the speci- 
men of A. speciosum as a variety grown under peculiar cir- 
cumstances, aud the short A. corbicula with the netted lid as 
