202 



THE VOYAGE OF H.M.S. CHALLENGER. 



network of sarcode, with wide oval and round meshes radiating irreguhirly from a 

 central point. The membrane is transversed by irregularly radiating ridges of firmer 

 sul)stance, which unite in the centre in a projecting boss at the point, where in this 

 specimen the ' glassrope ' has unfortunately been torn out. 



" In minute structure, Hyalonema toxeres corresponds in all essential respects with 

 Hyalonema sieholdii and Hyalonema lusitanicum. All the spicules are of the same 

 ground forms, with some little differences in detail, with the exception of one remarkable 

 spicule which enters largely into the structure of Hyalonema toxeres, and serves to 

 distinguish even the smallest portion of it. This is a large spicule, the largest above a 

 centimetre in length, and more than half a millimetre in width in the centre, shaped 



i'lQ. i>.—Myaionemato:ceres, Wyville Thomson. Upper (after 

 W. Th.) surface, natural size. 



Fig. 6.- 



-Hyahmema toxeres, Wyville Thomson. Lower (after 

 W. Th.) surface of the sponge, natural size. 



like a bow or boomerang. These spicules are distributed in all parts of the sponge, and 

 are particularly abundant near the insertion of the coil. No analogous form occurs in 

 the other species of Hyalonema. 



" The large amphidiscs are much larger than in any other known sponge. They are 

 upwards of half a millimetre in length and visible to the naked eye, twice as large as in 

 Hyalonema lusitanicum. The feathered shafts of the five-rayed sj^icules which fringe 

 the openings are longer than in the other species, and the rays of the cross are much 

 shorter (fig. 7). 



"The second specimen of the sponge body agreed with the one described in all 



