420 THE DEPTHS OF THE SEA. [CHAP. vn. 



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, H. 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 tho 

 most brilliant spun-glass, each thread from 30 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 Hyalonema. 



