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Zoology. — ''On the Structure of .^o me Siliceous Spicules of Sponges. 

 1. The stjli of Tetluja lyncurium, by Dr. G. C. J. Vosmaer 

 and Dr. H. P. Wijsman, Professors at the Leiden University. 



(Communicated in llic meeting ol' Api'il 22, 1905). 



After ScHWEiGGER (J 819) had denioiislrated that the spicules of 

 sponges in some cases do not consist of calcium carbonate. Grant 

 (1826) found them to contain silica, and Howerbank (1841 «) showed 

 that, in addition to the silica some organic matter is present. He 

 reached this conchision through the fact that the spicula when heated, 

 were partly carbonised. Kölliker (1864) remarked that the brown 

 or black colonr, produced by heating, is certaiidy not only due to 

 carbonised organic matter; examined in reflected light the heated 

 spicula appeal' white, and the dark spots seen in ti-ansmitted light are, 

 therefore, partly due to inclosed air. Thoulet (1884) found no 

 organic matter and concluded : "les spicules sont done constitués par 

 de la silice pure", which he compares with opal. Sollas (1885) 

 likewise finds that the silica resembles opal. It is now generally accepted 

 that the spicnles of siliceous sponges consist of some kind of opal ; 

 but that in some way or other, organic matter is also present. So far 

 here is a general agreement of opinion but the chemical analyses which 

 have been carried out show considerable differences as to the quantity 

 of water, combined with the silica as a gel. The formulae, given 

 for the composition \av\ from 2 {SiO.;) -[- Hj) to 5 (>SVO.,) + H^O, 

 but must be considered as mere failures. F. E. Schulze (1904) comes 

 to the result: "dass, entweder die Siphone keinen bestimmten kon- 

 stanten Wassergehalt haben, oder dass die organischen Zwischeidaniel- 

 len .... einen je nach der vorgtingigen starkeren oder gerijigeren 

 Austrocknung wechselnden Gehalt an Wasser haben". 



It is certain that even in the best cases, the quantity of organic 

 matter is so little that it cannot well be ascertained. Its presence 

 can, however, be proved by treating the spicules with hydrofluoric 

 acid. But there is also some disagreement as to the nature of this 

 matter and the exact place in the spicules where it is met with. 

 We shall see that different kinds of spicules vary in this point. 



In addition to the silica, which behaves like some kind of opal, 

 and which we propose to call spicopul, and the organic matter which 

 F. E. ScHULZE called spieuHne, — modifying the original term used 

 by Haeckel — in some spicules there have been found traces of 

 Na, K, 01, Fe, Mg and Ca, but in such slight quantities that they 

 can be left out of consideration for (he moment. 



