G. GORGONIA. 199 



tentacula of the animal ; when the borders of this 

 opening are smooth, we may either ascribe it to the 

 destruction of the tentacula, to their diminutiveness, 

 or to their possessing the retractile property to a 

 greater degree than the first mentioned. 



The Gorgonias vary consideraly in their form ; the 

 stem of some of them is wholly simple, devoid of any 

 ramification ; others have numerous branches, anasto- 

 mosed together, and forming a net-work of very 

 close meshes ; between these two extremes are found 

 a crowd of intermediates, forming a gradual chain of 

 union. 



The colour of the dried Gorgonia rarely exhibits 

 brilliant hues; but in the bosom of the sea it may be 

 very different. In the collections, some are found 

 white, some black, some red, green, violet, and yel- 

 low, almost always tarnished by the action of the air 

 and light, which are known to produce a very power- 

 ful effect on the colouring material of the Coralline 

 Polypidoms, even so far as to change or destroy it 

 almost instantaneously. 



The colour of the axe is not so variable as that of the 

 rind ; it is usually a deep brown, nearly black in the 

 opaque parts, and becoming a clear brown, fawn, or 

 even whitish, at the extremities, or in the parts where 

 the axe is transparent. In general the colour ap- 

 pears deeper in proportion as the axe is harder and 

 more horny. In the Gorgonias of which the axe is 

 pithy, it is whitish or yellowish ; this rule applies 

 pretty generally. 



Their size varies as much as their colour ; some 

 species scarcely reach five centimetres, whilst others 



