86 
COLOUR IN NATURE 
CHAP. 
corals belonged to it. The only other existing reef¬ 
building Alcyonarian coral is Tubipora , the organ- 
pipe coral ; here the coral itself is of a bright red 
colour, and the polypes either brownish-red with 
green-tipped tentacles, or entirely of a delicate green 
colour. 
Colour - resemblances in the Ccelentera 
We have already noted the plant-like habit of 
growth which causes so many of the simpler Coelentera 
to be popularly mistaken for seaweed, but there are 
also a few detailed resemblances which have been 
described. Thus the species of the sea-anemone 
genus Actinodendron have much-branched tentacles 
which resemble the fronds of seaweeds or ferns very 
closely. In the case of A. alcyonoideum the habitat 
is in sandy pools in the corners of coral rocks ; the 
long tentacles float freely in the water and sting with 
extreme severity when touched; the colour is dull and 
seaweed-like. It is suggested by Saville Kent that 
the resemblance to seaweed entices organisms within 
the reach of the deadly tentacles, and that this is 
therefore an example of “ alluring coloration.” A 
species of a related genus (Megalactes griffithsi ) has 
tentacles of similar nature, and inhabits similar 
situations, but is distinguished by a relatively elabo¬ 
rate system of coloration, being marked by radiating 
white lines on a ground of lilac, pale sea-green, 
gray and buff. Again, in the species of Heterodactyla, 
already mentioned for their elaborately beautiful fruit- 
like nematospheres, the branched tentacles are grass- 
green in colour and “ present the aspect of aggregated 
