Dr. J. E. Gray on Hyalonemata. 271 



from Dana, in which it is shown that as much as 23 per cent, 

 of silica is found in the Madrepores ; and silica is also found 

 in the axis of Gorgonia and other corals, forming an essential 

 part of their organic stnicture. (P. Z. S. 1867, p. 120.) 



Prof. Loven, who adopts Prof. Schultze's theory, that the 

 sponge is an integral part of the organism, when describing a 

 true sponge from the North Sea which he regarded as a Hyalo- 

 nemaj came to this conclusion from the study of the form and 

 structure of the Japan sponge as described by Prof. Schultze^ 

 which had been overlooked or not properly appreciated by 

 Prof. Schultze himself and other zoologists, myself among the 

 number, which, I think, fully prove that the sponge is not 

 affixed to marine bodies and placed at the base, but at the 

 apex of the glassy coil, the base of which he believes to be 

 affixed to some marine body, regarding the siliceous coil, as 

 seen in museum specimens, as only a fragment that has been 

 accidentally broken from its other fixed part. This latter 

 notion is inconsistent with what we know of the habits of the 

 genus, and also with the structure of the spicules of the differ- 

 ent specimens, which always taper towards the end in a most 

 uniform and regular manner, very unlike an accidental break 

 of a coil of spicules produced by an external force. 



Dr. Loven says that the circular holes on the outer surface 

 of the sponge (the chimneys or oscula of Prof. Schultze) 

 " cannot be the pores for the exterior current." But I think 

 that if he had been able to examine the sponge he would have 

 found that they are connected with the oscula in the internal 

 cavities of the sponge. (See Loven, Ann. & Mag. N. H. 1868, 

 ii. pp. 81, 89.) 



It was difficult to understand how what are here called the 

 " free " Hyalonemata keep themselves erect on the sea-bottom; 

 for it is clear they must do so, as the similar size and develop- 

 ment of the polypes show that they must be all equally within 

 the reach of food. (See P. Z. S. 1867, pp. 119, 902.) The 

 direction and manner in which the polypes on the apex are 

 developed shows that this cylindrical coral must be perma- 

 nently erect. 



It is quite possible that the Hyalonemata live with the sili- 

 ceous filaments sunk in the sand; and that might explain 

 why we have never seen, even in the most perfect and well- 

 developed specimens, the coil of siliceous spicules covered with 

 the polypes and the bark-like crust for more than half its length, 

 and that always on the upper part of the coil. 



A dealer, more than two years ago, showed me a number 

 of coils in the state in which he received them from Japan, in 

 which the exposed filaments of the coil were covered with 



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