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.] ; 
“9. 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 [. Steboldii and H. lusi- 
fanicum are found that never had any sponge connected with 
them (see species figured, Brandt, t. 1. f.15; 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 
Rope.’ [This character is common to the spicules of many 
sponges, and may be common to these and the spicules of Hya- 
lonema, 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. | 
I have been often told that Prof. Schultze has shown a 
series of spicules gradually passing from the form in the sponge 
to that im 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 peculiar 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. i. 19 
