22 



ous skeleton composed of spiciila of varying size and outline, 

 some like long threads of spun glass, a foot or more in length, 

 whilst others do not exceed the thousandth part of an inch. 



Tor the following description I am indebted to Mr. F. Kitten, 

 of Norwich, who writes. — "The Hyahnema, or 'glass rope' 

 sj)onge, was formerly supposed to Lelong to a class of organisms 

 called axiferous zoophytes, or barked corals. The ' glass rope,' 

 with its ' warty bark,' was supposed to have been distinct from 

 the sponge-like mass, forming the base, in which it appeared to 

 grow. Dr. Gray describes it as having a silicious axis : — ' The 

 axis formed of many twisted fibres, and its lower end, instead of 

 being expanded, is gradually tapering, and is parisitically 



embedded in a fixed sponge The joart above the 



base is in different specimens covered to a greater or less extent 

 (and evidently in the perfect state is entirely) with a kind of 

 jeathery bark, with truncated, ni2:)ple-shaped, scattered tubercles, 

 having flat crowns with radiating grooves and a central depres- 

 sion. In general the specimens are withdrawn and cleaned from 

 the spongy base, and the lower axis is cleaned ; but it appears 

 evident that they all are attached to such a sponge in their 

 natural state. The bark is formed of two distinct layers, the 

 outer layer having the appearance of an aggregation of grains of 

 sand, united together by a small quantity of animal matter ; the 

 inner layer having embedded in its substance numerous very fine 

 capillary fibres of precisely similar texture to those which form 

 the axis of the coral, but of much smaller size ; and this portion 

 of the bark evidently extends between and invests each of the 

 fibres of the rope-like axis. 



Dr. Gray's description is exact, so far as the external appear- 

 ance of the sponge is concerned ; but his surmise that the 

 so-called spongy base is a distinct organism recent observations 

 have proved to be incorrect. The basal portion is an integral 

 portion of the sjDonge, and, when growing, is uppermost, the 

 long fibres being buiied in the ooze, as in the allied forms 

 Phceronema (Holtenia) Carpenteri and Phceronevia Gray HP 



As before observed, the earliest known specimens of this 



