33 



fragments of them with a power of 300 linear, I was much surprised 

 to find many of them with well developed spicula embedded in the 

 centre of the horny fibres ; and on extending my observations to other 

 species, I found that there were few or none of these keratose sponges 

 in which spicula were not to be detected in some of the fibres ; al- 

 though it often required a considerable degree of patient research to 

 find them, and very frequently the first intimation of their presence in 

 the sponge, was only to be obtained by burning, comparatively, a 

 considerable mass before the blow-pipe, subjecting the ash to the ac- 

 tion of dilute muriatic acid, and then examining the residue. But in 

 all cases where their presence was thus detected they were afterwards 

 by patient investigation found in situ. 



From the results of the examination of the Australian species I was 

 naturally led to suspect that siliceous spicula might possibly be de- 

 tected in the sponges of commerce ; and that I might investigate them 

 as nearly in their natural state as circumstances would permit, I ap- 

 plied to a large importer of sponges, who very kindly supplied me 

 with the species and varieties of the sponges of commerce, before they 

 had undergone the usual process of cleaning and bleaching. 



The principal sources for the supply of the European market with 

 sponge is the Mediterranean and the West India islands, and espe- 

 cially the Bahamas. The former is of a finer texture than the latter, 

 and is designated Turkey sponge. Upon carefully examining a con- 

 siderable number of specimens of this description with the microscope, 

 I found two well-marked species. The West Indian sponge also 

 proved to be a species distinct from either of the Turkey ones. 



The two species of Turkey sponge are so similar in external cha- 

 racter as to render it impossible to distinguish them from each other 

 by a superficial examination ; but in their anatomical structure there 

 is a distinct and very striking difference. The common form — the 

 Spongia officinalis of Lamarck — is so familiar to every one as to ren- 

 der a lengthened description of its external characters unnecessary j 

 but it must be remarked that in the state in which we usually receive 

 it, it has been carefully cleaned by maceration in water or a weak so- 

 lution of acid, from all remains of the mucous or fleshy coating of the 

 horny fibre ; and if we examine a fragment of such a specimen be- 

 neath the microscope, we shall perceive the fibres to be totally free 

 from all remains of this fleshy coat, and in this state it has the appear- 

 ance of a smooth light amber-coloured fibre : but if we examine a 

 specimen which has not been thus treated, the thread, especially that 

 of the interior of the sponge, is seen to be coated with a thin and 



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