88 On the "Glass-Rope" Hyalonema. 



and usually the spicules are scattered loosely among the 

 threads,, though in some cases the spicules are contained 

 within the threads ranged along their centre. In all these 

 cases the sarcodic living matter coats and surrounds both the 

 threads and spicules. In some silicious sponges, however, 

 the horny substance, in its firm condition, is entirely wanting, 

 and the skeleton seems to be made up of silicious needles 

 alone, with incrusting soft incoherent protoplasm. Hyalonema 

 seems to be nearly in the latter condition, for a structureless 

 film only, easily soluble in caustic potash or soda, coats and 

 connects the spicules of which its framework is built up. The 

 interior of the sponge is formed of a loose irregular network 

 of threads of interwoven needles. Towards the base of the 

 sponge there are several large irregular openings nearly half 

 an inch wide, leading into passages lined by an open imperfect 

 membrane of meshed spicules. Within the sponge these 

 passages divide and pass into connection with a sort of lacunar 

 system, which communicates with the round apertures opening 

 externally on the surface of the sponge. 



The lower end of the silicious coil penetrates the sponge 

 vertically nearly to its base. After entering the sponge it 

 becomes slightly thicker for an inch or so, and then rapidly 

 diminishes to an extremely fine produced point. The needles 

 of the coil are here intimately interwoven with the ordinary 

 spicules of the sponge which pass in among them. The cord- 

 like fibres of the sponge-mass flatten out as they approach the 

 coil, and the so-formed irregular plates are felted -as it were 

 into the coil vertically between and upon its outer needles, so 

 that the arrangement of the tissue of the sponge bears an 

 evident relation to the position of the silicious axis. 



The connection between the body of the sponge and the 

 lower end of the coil is so close that considerable violence is 

 necessary to separate them ; indeed, it is absolutely impossible 

 to do so completely without injuring the infinitely delicate 

 ends of the long needles. This circumstance alone, although 

 it may not be conclusive against the parasitical nature of the 

 sponge, entirely disproves the artificial arrangement of the 

 needles of the coil. 



The form of the silicious spicules which build up the tissues 

 of the body of the sponge is most varied. Most abundant, 

 interlaced to form the great bulk of the threads of the spongy 

 texture, and accumulated especially towards the surface, are 

 long spindle-shaped needles about a line in length. These 

 spicules (Plate, Figs. 4 and 5) arc frequently smooth, and 

 pointed at both ends ; but sometimes one end is pointed and 

 the other clubbed, and very frequently cither one end or both 

 ends, or the whole length of the needle, is studded with short 



