THE CCELENTERATES 



129 



radiating partitions. Some, also, develop a hard, stony skeleton 

 by secreting carbonate of lime obtained from the water in which 

 they live. 



We often see, when collecting on the beaches of rocky coasts, 

 and especially after storms, a number of vegetable-like growths, of 

 a greyish or brownish colour, each consisting of one or more main 



FIG. 79. Sertularia filicula 



stalks bearing a number of delicate branches. Some of them, by 

 their peculiar mode of growth, have suggested the name of sea firs, 

 and a few of these, together with other animals of the same group, 

 may readily be recognised by the accompanying illustrations. They 

 are the objects already referred to as being commonly included in 

 collections of sea-weeds by young naturalistb, but they are in reality 



K 



