194 



CORALS 



found in masses as big as a " boy's head " on the Scottish 

 and other coasts of Great Britain. It seems to be fond of 

 situations in which there is a good flow of water, and has 

 been found choking the supply pipes of an aquarium.^ 



The mass is built up of an immense number of small 

 branching calcareous tubes about 0-5 mm. in diameter, and 

 is hone3'combed with irregular spaces which harbour various 

 kinds of marine creatures (Fig. 100). It is not hard, as 

 coral substances usually are, but delicate and friable, and 

 unless handled with care breaks up into minute fragments. 



The appearance of the living colonies of Filograna has 



Fig. 99. — Filograna implexa. \ nat. size. 



been described by Professor Mcintosh" as follows : " Fresh 

 examples from Plymouth in sea-water, as Huxley and others 

 truly said, resemble corals in so far as the branchial fans 

 of the annelids project from the tips of the tubes as miniature 

 flowers, the distal parts (branchiae) of which are pale greenish 

 yellow and the anterior region of a fine reddish hue which 

 tints the cephalic region at the base of the branchiae and 

 passes a short distance along each filament. When eggs 

 are present the posterior region is also reddish, the colour 

 of these being of a brighter hue than the front. Two dark 



^ Prof. Mcintosh, " Notes from the Gatty Marine I^aboratorj', St. 

 Andrews," (xhi.), Ann. Nat. Hist, iii., 1919. 

 ^ I.e. p. 149. 



