156 Prof. M. Schultze on Hyalonema, 



to regard the sponge at the lower extremity of the "Glass Rope " 

 as something jo^/ec^/?/ constant. 



I now come to the last, but very important, point, the micro- 

 scopic examination of the spicules of the sponge. Dr. Gray says 

 (/. c. p. 292), " Prof. Max Schultze enters into a long description 

 of the spicula of the sponge, and figures several of them ; but I 

 cannot see what bearing that has on the subject ; for he does not 

 show that any spicula of a true sponge are like the spicula that 

 form the axis of the coral. They certainly have little affinity to 

 the elongated siliceous spicula of the genus Alcyoncellum or 

 Eupledella, with which they have been compared.^' But in 

 reality my " long " description of the spicules of the sponge in- 

 cluded the incontrovertible proof of the mutual relation of the 

 latter and the " Glass Rope,^' and places it beyond a doubt that 

 the nearest allies of Hyalonema are the Euplectell(2 [Alcyoncellum 

 Quoy & Gaim.) from the Philippines, which are to a certain 

 extent similar even in external form. 



The proof lies in the form and intimate structure of the 

 spicules of the inferior sponge. Notwithstanding great external 

 differences, all these spicules have something in common which 

 is wanting in the spicules of other sponges, and therefore sharply 

 characterizes the Hyalonema-siponge. This is the peculiarity 

 that the longitudinal canal presented by the spicules possesses 

 one or two perpendicularly placed transverse canals almost 

 exactly in the middle. Very frequently the spicules, at the 

 point where these short transverse canals are situated internally, 

 show externally perceptible thickenings, which may grow out 

 into longer lateral branches; and by this means are produced the 

 numerous cruciform spicules figured by me, and so characteristic 

 of the Hyalonema-siponge as to furnish a diagnostic character 

 even for the inconsiderable traces of the sponge which often 

 alone remain in imperfectly preserved specimens. In other 

 cases the external dilatations or lateral branches at the locality 

 of the transverse canals are entirely wanting ; but by careful 

 examination the transverse canals themselves may always be 

 found, even in the perfectly smooth awl-shaped spicules (see taf. 

 iii. fig. 1 of my monograph). 



But if this structure be characteristic of the whole of the 

 spicules of the sponge of Hyalonema, it might be expected that, 

 if the long threads (as can no longer be doubted) be parts of 

 this sponge, it will also occur in these long threads of the "Glass 

 Rope.^' On account of the difficulty of finding any fine trans- 

 verse canals that might be present about the middle of the 

 longest spicules, which measure from one foot to a foot and a 

 half in length, I looked out the shortest threads of the " Glass 

 Rope.^^ They occur in the inferior extremity, which is enveloped 



