AtCYONIITM. 93 



the polyps, and they undoubtedly possess many features of 

 general resemblance to the well-known fresh-water polyp 

 Hydra. A critical examination of the anatomical 

 structure of the Alcyonarian, however, proves that the 

 name " polyp " is misapplied in this case, for the bodies 

 referred to only correspond with a part of the polyp of 

 the Hydra, namely, the free end with the crown of 

 tentacles, the greater part of the fixed or proximal end 

 of the Alcyonarian polyp being buried in the massive 

 substance of the coral. We have, in other words, two 

 parts in the body of the Alcyonarian polyp, — (i.) a part 

 which is free and can be retracted or expanded at will, 

 and (ii.) a part which is attached and firmly welded to the 

 corresponding parts of neighbouring polyps. 



With this explanation of the general structure the 

 reader is prepared to understand the critical or diagnostic 

 features by which a given specimen may or may not be 

 referred to the Order Alcyonaria. 



The Alcyonakia are Coelenterata which (with 

 one or two rare exceptions) form colonial 

 organisations by budding. The individual polyps 

 composing the colony are provided with eight 

 tentacles at their free extremity, and each of these 

 tentacles is provided with two or more rows of 

 papilliform processes called pinnules, giving the 

 tentacles a feathered or pinnate form. 



The form which the Alcyonarian colony takes varies 

 immensely in the different families into which the Order 

 is divided ; some being encrusting plates, some lobular in 

 form, some shrubby, some mushroom shaped, and so on, 

 but a detailed description of these forms would take me 

 beyond the scope of this memoir. The important point to 

 note here, however, is that although there is a remarkable 



