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 
