Prof. M. Schultze on Hyalonema. 157 



by the sponge, of not more than a few millimetres in 

 length. That, nevertheless, they are related to the long threads 

 is shown by their great thickness, in which they agree precisely 

 with the thinnest of the long threads. These are indubitable 

 intermediate structures between the short spicules of the sponge 

 and the long ones of the " Glass Rope.''' These short, thick 

 spicules are rare; but the few examples of them which I found 

 were quite sufficient to establish the correctness of my supposi- 

 tion. About the middle of the space between the two pointed 

 ends they possess the characteristic fine transverse canals of the 

 axial canal quite distinctly, although externally not the slightest 

 dilatation of the spicules is to be observed at the spot in question 

 (see taf. ii. fig. 6 of my book). After this favourable result I also 

 examined the longer spicules, and had the good fortune to discover 

 the short transverse canals in fragments of the middle of these 

 mounted in Canada balsam. 



Thus, therefore, we have every imaginable proof of the 

 mutual relation of the ^^ Glass Rope ^' and the sponge, which 

 may be briefly recapitulated as follows : — 



1. The long siliceous threads are in structure indubitable 

 sponge-spicules. They must therefore have been produced in a 

 sponge. 



2. Such a sponge, likewise with siliceous spicules, occurs 

 constantly at the lower extremity of the " Glass Rope " in or- 

 ganic connexion therewith. Even when the '^ Glass Rope " is 

 injured and smeared with cement (" Kitt ") the traces of the 

 sponge may be detected if only a portion of the inferior finely 

 pointed ends of the long siliceous threads is preserved. 



3. The sponge at the lower extremity of the long threads has 

 very characteristically constructed spicules, inasmuch as their 

 axial canal always possesses one or two perpendicular transverse 

 «anals. The same characteristic structure is also displayed by 

 the longer and shorter threads of the " Glass Rope.'' 



The following important circumstance must still be mentioned. 

 Of all known Sponges only the rare and extraordinarily elegant 

 Euplectella (Owen) from the Philippines is somewhat allied to 

 Hyalonema in external form. These Euplectella consist of a 

 sponge-body composed of beautifully interlaced siliceous spicules, 

 and cylindrical in form, from the upper end of which projects a 

 tuft (a cord) of long, silky, thin siliceous spicules, in which 

 Bowerbank has found threads of 3 inches in length. I have 

 examined perfect specimens of Euplectella in Leyden, and I 

 found that even in the intimate structure of its spicules it very 

 closely agrees with Hyalonema. In fact the most important 

 character of the spicules of Hyalonema^ namely the single or 

 double transverse canal of the axial canal, is reproduced in Eu- 



