356 MR. GEOEGE BROOK ON" THE 



united is not so intricate as in Madrepora. In lobose species of 

 Porites the centre of eacli lobe consists of an open network o£ 

 tissue, and the peripheral parts in which the corallites are im- 

 bedded has a similar structure, but the corallites are shallow and 

 differ considerably in structure from those of Montipora. In 

 Porites and its allies the budding may be inter- or intra-calicular 

 and the corallites remain in direct communication with one 

 another. Owing to the fact that the walls of adjoining 

 corallites become fused together, there is little or no coenen- 

 chyma between them. In the case of Turhinaria budding 

 takes place by means of serial, radially-directed stolons, each 

 more distal corallite being directly connected with the base of 

 the one behind it. The radiating series of corallites are connected 

 together by true ccBnenchyma. 



It will next be necessary to give a short summary of the 

 structure of the soft tissues so far as this is known at present. 

 Fowler has studied two ' Challenger' species, in one of which an 

 interesting and new type of dimorphism occurs. The following 

 short summary of his results gives the chief points of interest 

 for my present purpose. 



1. The external body-wall consists of ectoderm, raesogloea, and 

 entoderm. Under this and between the costse a series of external 

 longitudinal canals exists, which open into each other and also 

 through the corallum into a series of internal canals with radial 

 and transverse connections ; these in turn communicate with the 

 general coelentera of the polyps, and all communicate eventually 

 with the coelenteron of the axial polyp. 



2. The structure of the polyps is in its general features 

 Aetinian, but there is a marked bilateral arrangement of the 

 parts. The septa are probably entocoelie. There are twelve 

 mesenteries ; six are short, the others longer, but two of these 

 are very long and are the only ones which bear reproductive 

 organs. Similar elongate mesenteries occur in Alcyonaria, in 

 Antipatharia, and in Seriatopora and Pocillifera amongst the 

 Madreporaria. In Antipatharia, as in Madrepora, they are the 

 only ones which bear reproductive organs. 



Since the publication of Fowler's observations, our views as to 

 the homologies of the mesenteries of Z.oantharia have undergone 

 considerable modification, due more especially to the researches 

 of Haddon and McMurrich on Actiniaria and my own on Anti- 

 patharia. Fowler's division of the peripheral portions of the 



