420 THE DEPTHS OF THE SEA. [CHAP. 1X. 
Off the Butt of the Lews, in water of 450 to 500 
fathoms, we met on two occasions with full-grown 
specimens of a species of the remarkable genus 
Hyalonema (Fig. 66), with the coils in the larger 
examples upwards of 40 centimetres in length. 
Hyalonema is certainly a very striking object; and 
although our specimens belong apparently to the 
same species, 17. lusitanicum, which has already been 
recorded by Professor Barboza du Bocage from the 
coast of Portugal, it is one of the most interesting 
additions made to the British fauna during our 
cruise. 
A bundle of from 200 to 300 threads of trans- 
parent silica, glistening with a silky lustre, like the 
most brilliant spun-glass,—each thread from 80 to 40 
centimetres long, in the middle the thickness of a 
knitting needle, and gradually tapering towards either 
end to a fine point; the whole bundle coiled like a 
strand of rope into a lengthened spiral, the threads of 
the middle and upper portions remaining compactly 
coiled by a permanent twist of the individual threads ; 
the lower part of the coil, which, when the sponge is 
living, is imbedded in the mud, frayed out so that the 
glassy threads stand separate from one another, like 
the bristles of a glittering brush; the upper portion 
of the coil close and compact, imbedded perpen- 
dicularly in a conical or cylindrical sponge; and 
usually part of the upper portion of the silicious 
coil, and part of the sponge-substance, covered 
with a brownish leathery coating, whose surface is 
studded with the polyps of an alcyonarian zoophyte : 
—such is the general effect of a complete specimen 
of EHyalonema. 
