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150 CLASS JII.-^ORDER I. 



able ; in the thickness of the fibres, for instance, some 

 of them resemble the Antipathes, having their branches 

 anastomosised, whilst others are composed of fibres 

 as fine as the threads of silk, and wove as close as 

 down, or the hair of beaver when formed into hats ; 

 every intermediate gradation between these two ex- 

 tremes is to be met with. 



In the texture of the Spongias it is also observable 

 that they have their holes of difierent sizes and depths, 

 sometimes regularly and sometimes irregularly dis- 

 posed : of the use for which these holes (vvhich hence- 

 forth we shall denominate oscules) are designed, we as 

 yet remain ignorant ; but observation leads us to con- 

 clude that they answer the purpose of introducing 

 water into the central parts of the Polypidom ; so that 

 if there are any polypi internally, they may be sup- 

 plied with the necessary aliment. There are however 

 many Spongias destitute of these oscules ; the absence 

 or presence of which, together with their form and si- 

 tuation, may assist in furnishing us with criteria for 

 defining the several species : the same may be said of 

 the variety in their texture. 



I can say nothing decisive as to their colours ; they 

 appear varied, but fugitive ; those authors who have 

 been enabled to observe them in a living state, men- 

 tion the colours as being numerous and bright. The 

 few I have seen on the coasts of Calvados, when 

 first taken from the sea, exhibited a beautiful red, or a 

 bright citron ; those dried, in collections, present us 

 with every hue from a dirty white to a deep black, 

 passing through fawn-colour and every intermediate 

 shade. 



Their height varies from a millemetre to a complete 



