SPONGE-SPTCULES I HYALONEMA. 529 



Manilla Seas ; which, for some time one of the greatest of zoological 

 rarities, has now been found in sufficient abundance to allow every 

 Microscopist to acquaint himself with its beautiful structure.* — 

 Another extraordinary production, which is probably to be referred 

 to the same type, is the Hyalonema, originally brought from the 

 Japan seas, but since found upon the coast of Portugal and elsewhere. 

 This consists of "a bundle of from 2- to 300 threads of transpa- 

 rent Silica, glistening with a satiny lustre, like the most brilliant 

 spun-glass; each thread about eighteen inches long, in the middle of 

 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 

 lower portions remaining compactly coiled by a permanent twist of 

 the individual threads ; the upper portions of the coil frayed out, 

 so that the glassy threads stand separate from one another, like 

 the bristles of a glittering brush ; the lower extremity of the coil 

 imbedded perpendicularly in the middle of a hemispherical or 

 conical undoubted Sponge, and usually part of the exposed portion 

 of the siliceous coil and part of the sponge covered with a brown 

 leathery coating, whose surface is studded with the Polypes of an 

 equally undoubted Zoantharian Zoophyte, "f — There are many 

 Sponges, on the other hand, in which no fibrous network can be 

 discerned, the spicules lying imbedded in the midst of the sarcode- 

 mass ; such is the case in Grantia (Fig. 271 a), whose triradiate 

 spicules are composed of Carbonate of Lime. — Sponge-spicules are 

 much more frequently Siliceous than Calcareous ; and the variety 

 of forms presented by the Siliceous spicules is much greater than 

 that which we find in the comparatively small number of species 

 in which they are composed of Carbonate of Lime. The long 

 needle -like spicules (Fig. 273), which are extremely abundant in 

 several Sponges, lying close together in bundles, are sometimes 

 straight, sometimes slightly curved ; they are sometimes pointed at 

 both ends, sometimes at one only ; one or both ends may be fur- 

 nished with a head like that of a pin, or may carry three or more 

 diverging points which sometimes curve-back so as to form hooks 

 (Fig. 390, h). When the spicules project from the horny frame- 

 work, they are usually somewhat conical in form, and their surface 

 is often beset with little spines, arranged at regular intervals, 



* See Prof. Owen in "Transact, of Zool. Soc," Vol. iii., p. 203, and in 

 "Transact, of Linn. Soc," Vol. xxii., p. 117 ; Dr. J. E. Gray in "Popular 

 Science Review," Vol. vi.,p. 239; and Mr. H. J. Slack in "Intellectual 

 Observer," Vol. xii., p. 161. 



t See Prof. Wyville Thomson in the "Intellectual Observer," Vol. xi., 

 p. 81.— The nature of this organism has been the subject of much contro- 

 versy, of which a resume is given in the Paper just referred to. The 

 Author agrees with Prof. Max Schultze and Prof. Wyville Thomson in 

 regarding it as essentially a Sponge on which a Zoophyte is parasitic ; 

 whilst Dr. J. E. Gray maintains that the 'flint-rope' is the stem of an 

 Alcyonarian Zoophyte, and Dr. Bowerbank regards the whole as a Sponge, 

 of which the so-called Polypes are the oscula. 



H M 



