428 
THE VOYAGE OF H.M.S. CHALLENGER. 
Remarks. — The faithful description and illustrations given by Perceval Wright of 
this sponge render its identification an easy task. Two fine specimens, both in an 
excellent state of preservation, are in the Challenger collection, a fortunate circumstance, 
considering the deplorable loss of the type vrhich was sent to Weimar, never to return. 
The tylote chiasters, which are very frequently sexradiate triaxons, are met with 
also in Tethya maza, Sk., Tethya ingalli, Bwk., and Tethya jajponica; the remarkable 
cladose asters of the choanosome are more characteristic ; but similar spicules occur in 
Tethya ingalli, Bwk., which is distinguished by its completely fibrous cortex. A si mil ar 
representative spicule occurs in Tethya maza, but is distinguished by the form of the 
actines, which are cylindrical, shorter, and generally roughened. In Tethyoj japonica 
cladose asters are absent, and as far as I can make out unrepresented. The alliance of 
Tethya maza, Tethya seychellensis, Tethya japonica, and Tethya ingalli is unquestionably 
very close, and as regards the first three, I am inclined to regard them as varietal modi- 
fications of a single species. 
The specimen of Tethya seychellensis from Samboangan has a very different external 
appearance to that from Station 186, a difference which depends on a difference in the 
size and form of the conules and condition of the oscule. The specimen from the latter 
station is 31 mm. by 26 mm. in length and breadth by 24 mm. in height ; it is attached 
by a broad base, and presents a single oscule situated at the summit. The oscule is 
widely open, about 6 mm. in diameter, and surrounded by a membranous margin ; it 
leads into a cloaca which receives some five or six somewhat large excurrent canals. The 
texture is loose. Most of the conules are very small, under 1 mm. in diameter, and they 
present a very interesting series of variations, which may serve to explain the differences 
of appearance presented by different specimens of Tethya lyncurium, differences so great 
that they seem at first sight of specific importance. Here these differences are united 
in perfect gradation in one and the same individual. In the simplest case the conules 
are small and conical, and marked by lateral rounded ridges which radiate from the 
summit, and pass continuously into similar ridges proceeding from adjacent conules, thus 
forming a network with polygonal, frequently triangular meshes (PL XLIV. fig. 7). 
Within these meshes the surface is depressed and occupied by a pore-sieve. The appear- 
ance thus produced is somewhat similar to, but not quite identical with, that so well 
represented by Schulze in his account of Aphysilla aerophoba, N.^ 
In the next stage the ridges about the sides of each conule have increased in breadth, 
and present a flattened upper surface. As this change commences from the conule and 
extends outwards, so the middle part of the ridges remains for some time unaffected and 
contrasts by its smooth rounded upper surface with the flat scar-like summit of the region 
nearer the conule ; in other words, each conule is now surrounded with its own system of 
flattened ridges, but these remain connected with those of adjacent conules by a bridge of 
^ Zeitschr.f. ydss. Zool., Bd. xxx. pi. xxii. figs. 4-6. 
