GENERAL MORPHOLOGY. 



In the present section I propose to give a general outline of the structure of the 

 various genera of Antipatharia, more especially with regard to the form of the zooid and 

 the number and relative development of the mesenteries. On account of the previous 

 want of information on the subject, it will also be interesting to consider generally the 

 bearing of these preliminary observations on the relationship of the Antipatharia to other 

 Zoantharia. 



The Antipatharia are all colonial in habit, and the corallum is usually fixed by a 

 dilated base to some foreign object. Some species are parasitic, and it seems probable 

 that in the ancestors of the Antipatharia this feature was more frequent than in living 

 types. The production of a colony from the original oozooid developed from an ovum 

 has not been studied, but it is probable that this takes place by budding. The colonies 

 consist of blastozooids united together by ccenenchyma, the whole of the soft tissues being 

 supported on a central horny axis. The zooids of the Antipathida; are all constructed on 

 the same plan, but amongst the genera examined there is a gradual specialisation in 

 one direction, corresponding to a physiological division of labour, and finally resulting 

 in dimorphism. 



In an ideal case the zooid is more or less rounded in outline, and consists of a short 

 hollow cylinder projecting beyond the surface of the ccenenchyina for no great distance. 

 The peristome usually bears a central conical projection, on the surface of which the 

 mouth is situated. The tentacles are six in number; they are arranged radially in zooids 

 with a rounded outline, but in many cases there is a more or less well-marked arrange- 

 ment in longitudinal rows, due to elongation of the zooid in one direction. The body-wall 

 is not separated from the peristome by a well-marked "margin," as in typical Actiniaria, 

 and passes imperceptibly into the ccenenchyma. The oral cone often shows on its inner 

 margin a number of crenate folds, which are partially everted portions of the stomodseum, 

 each fold occupying the space between two mesenteries. In other cases the surface is 

 quite smooth. The mouth leads through a short stomoda?um into the ccelenteron. The 



