46 



NATURAL HISTORY OF OUR SHORES 



to rocks and sea-weeds. In shape it varies considerably, 

 but is usually in ramifying, stag's -hornlike branches, of 

 a grey or pale brown colour, and of a soft, pulpy feel. 



Fig. 17 represents a small portion of this latter with the 

 polypi expanded, and Fig. 18 is a micro-photograph of a 

 thin section cut through a small portion, just below the 

 level of the tentacles of the polypi. 



The mesenteries, described a page or two back, as a 



Fig. 17. Small portion of Alcyonium digitatum, with 

 the polypi extruded. About 8 diameters 



characteristic of Anthozoan anatomy, are here seen at the 

 part where they radiate from the inner walls of the column 

 to the oesophagus, and in the matrix are seen the spicules of 

 carbonate of lime (shown in larger size in Fig. 17). 



These forms are of interest as illustrating the structure 

 of corals ; for it has been shown that all these, even the solid 

 red coral (Corallium rubrum) of the Mediterranean, so much 

 used in jewellery, etc., is formed by the fusion of spicules 

 such as those existent in Alcyonium. 



