Dr. J. E. Gray on Hyalonemata. 269 



" 1. The long siliceous threads are in structure indubitable 

 sponge-spicules. They must therefore have been produced in 

 a sponge." [I have shown that in structure and function they 

 are unlike any sponge-spicules known. See Ann. & Mag. Nat. 

 Hist. 1868, i. p. 292.] 



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

 constantly at the lower extremity of the ^ Glass Rope,' in 

 organic connexion therewith." [Bocage and I have shown 

 that many most perfect specimens of H. Sieboldii and H, lusi- 

 tanicum are found that never had any sponge connected with 

 them (see species figured, Brandt, t. 1. f. 1 ; t. 2. f. 6), though 

 Dr. Max Miiller regards the sponge as something permanently 

 constant.^ 



" 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 canals. The same characteristic structure is also 

 displayed by the longer and shorter threads of the ^ Glass 

 Eope.' " [This character is common to the spicules of many 

 sponges, and may be common to these and the spicules of Hya- 

 lonemaj which, as stated above, differ from the spicules of all 

 known sponges in the structure of the end and in their mode of 

 growth and function. The reason why I did not refer to this 

 point in my former paper is that I did not, and even now do. 

 not, regard it as so important as Prof. Schultze seems to con- 

 sider it. The existence of a transverse canal being common 

 to siliceous spicules of a sponge and of Hyalonema did not 

 appear to me to decide that the latter were not secreted by a 

 polype. The value of microscopic observations depends on 

 the accuracy and knowledge of the observer ; and we must not 

 decide beforehand that a siliceous spicule with a transverse 

 canal cannot be secreted by a polype because we have not be- 

 fore observed one, especially when the spicule has other cha- 

 racters that separate it from all sponge-spicules, as is the case 

 with the long spicule of the coil of the Hyalonema.l 



I have been often told that Prof. Schultze has shown a 

 series of spicules gradually passing from the form in the sponge 

 to that in the coil. I cannot find any one showing any 

 passage from one to the other, nor the slightest approach to 

 one with the ring of spines, or the pecuHar appearance of the 

 end or fracture. There is a considerable difference in form 

 between the cruciform spicules of the sponge at the base and 

 that on the bark-- so great as to have induced Brandt to call 

 one Spongia spinicrux and the other Spongia octancyra ; yet 

 probably the sponge on the bark is only an extension of the 

 sponge at the base, like the sponge found between the ends of 



Ann, & Mag, N. Hist. Ser. 4. Vol. ii. 19 



