GROWTH OF THE CORAL COLONY 97 



the same. MontijJoiw vary from yellow to olive-groen and 

 brown, and yet tlie zooid is always of the same sulphur-yellow, 

 and the coral is always identical in other respects. 



The general coloration of the coral body cannot therefore 

 be regarded as specific, and the coloration of the zooids also 

 shows a strange inconstancy. Although, as a rule, the zooids 



Fig. 31. 



Colourless Stylojjora Colony trom Deep Water 

 (8-12 Fathoms). 



When growing in more shallow water its branches are brownish yellow. 



of different colonies of identical species — though the colonies 

 may be very different in appearance — are similar, yet in one 

 colony the individual zooids may be very variously coloured. 



There is one very striking case, which is not uncommon in 

 the atoll, of an Astrcea, where the zooids on the upper surface 

 are a fine fluorescent green, at the sides of the growth brown, 

 and below white. And here it would appear — as also probably 

 in the deeper water forms — that light had some influence on 



