25 
1913-14.] Siliceous Sponge of the Order Hexactinellida. 
Others were much smaller, 0‘2 mm. between their tips, and in many five or 
six rays could be seen, one or two of which had been broken across at or 
near the common centre ; the type, therefore, was hexact. In the middle of 
the centre was a very minute circle, from which a line passed along the axis 
of each ray almost to its tip. The rays were sometimes smooth, but more 
usually slightly roughened near the tip and faintly serrated at the sides. 
Mingled with the ray-like spicules were numerous disc-shaped Diatoms, 
which varied in their dimensions from 77 to 96 /u across the face of the 
disc. They had doubtless lived in the mud in which the basal tuft had 
been anchored. 
As the siliceous sponges have been described by Professor F. E. Schulze 
in an elaborate memoir in his Challenger Report on the Hexactinellida,* 
I have examined the text and figures so as to identify, if possible, the 
species from the characters presented by the basal spicules. The length 
and thickness of the tufts and the number of spicules varied materially in 
different genera and species, but in the genera Hyalonema and Pheronema 
species existed in which the basal tuft of spicules attained a considerable 
length. Schulze gave as a character of Hyalonema a tuft consisting of 
long and strongly developed basal spicules which projected downwards 
from the centre of the lower end of the body, and the spicules themselves, 
either wholly, or for the most part, had four-toothed anchors. He stated 
that in H. sieboldii the total length of the body and tuft varied from 50 
to 80 cm., and as the body occupied 10 to 15 cm. of that length, the basal 
tuft varied from 30 to 60 cm., and broke up at the lower end in a brush-like 
manner. This species inhabits the seas of Japan. In H. affine the tuft 
was 47 cm. long, but only 8 mm. broad. Wyville Thomson dredged in the 
sea north of the Butt of Lewis, from a depth of 450 to 500 fathoms, 
Hyalonemata in which the root tuft measured 40 cm. or more. In Phero- 
nema carpenteri, obtained in the sea north of Scotland, as well as off the 
coast of Brazil, a number of slender tufts, only 1 to 2 mm. in breadth, the 
spicules of which were 30 to 40 cm. long, interlaced abundantly in the felt- 
work of the basal tuft. Wyville Thomson considered that in the larger 
specimens the tufts may measure several decimetres. Schulze stated that 
other species of this genus also possessed long basal spicules. 
Schulze has figured Numerous examples of four- and six-rayed spicules 
in the bodies of the sponges in the Hexactinellida group. In my specimen 
the rayed spicules found in the basal tuft did not properly belong to it, 
but had accidentally become intermingled with the basal spicules. Schulze 
specially referred to the lower end of the body of Hyalonema as containing 
* Yol. xxi. part 53, 1886. 
