ALCYONARIAN CORALS 107 



the corals have very much the same general colour in the 

 sea as they have when dried and stored in a museum. 



There are, however, some exceptions to these general 

 rules (see Primnoa, p. 129, Tubipora, p. 112). 



In the Madreporaria, on the other hand, the colours are 

 almost invariably due to a pigment diffused through the soft 

 tissues which is soluble in alcohol and fades away soon after 

 the death of the corals. Dried and preserved Madreporarian 

 corals, therefore, never show the nature of the brilliant 

 colours they may exhibit when they are alive. 



It is interesting in this connexion to notice the difference 

 there is between the exhibits in the cases of a museum of 

 the Alcyonarian and Madreporarian corals. On the one 

 hand, we have an endless variety of bright colours and on 

 the other a monotonous dull stony white. 



CoRALLiUM.^ — The first coral mentioned in literature; 

 and the most famous throughout the ages for its beauty and 

 for the occult powers it was supposed to possess, is the red 

 or precious coral of the Mediterranean Sea. In another 

 chapter will be given a short account of the history of the 

 trade in this substance and of the myths concerning its 

 origin and properties. Here we are only concerned with the 

 study of the red coral from the zoological point of view. 



The hard red coral substance that is sold in the shops 

 is the axis or central supporting core of a dimorphic colony 

 of Alcyonarian polyps. When the coral is alive, this axis is 

 covered by a soft bark or crust, through which penetrates an 

 elaborate system of canals, which bring the two kinds of 

 polyps, the Autozooids and Siphonozooids, into communica- 

 tion with one another (Fig. 46). 



When a colony of Corallium that has been just removed 

 from the sea is placed in a glass vessel and allowed to remain 

 there for a little while, the white and almost transparent 

 autozooids gradually expand and project from the surface 

 of the bark, producing an effect which the earlier naturalists 

 mistook for the flowers of a plant (Fig. 47). Each autozooid 

 bears a crown of eight pinnate tentacles, formerly regarded 



1 See the beautifully illustrated memoir by H. de Lacaze-Duthiers, 

 Histoire naturelle du Cor ail, Paris, 1864. 



