SUMMARY OF RESULTS. 



The present volume has dealt with a single genus as exhaustively as the material * and the 

 opportunities of studying it have allowed. 



The result has been a considerable advance. The essential characters of the genus have 

 been discovered, and the genera Rhodarcea, Tichopora and Litharcea have been shown to 

 belong to it. 



It is now possible to trace the genus back through time, at least to the Cretaceous period, 

 and to follow some of the shiftings of its distribution. 



The relationship of the genus to Porites, which, with Goniopora, constitutes the family 

 Poritidre, has been provisionally defined, and the view that the two families, Poritidse and 

 Madreporidse, had a common origin from the simpler Eupsammiids, which was suggested by 

 the system of Milne-Edwards and Haime, has been rendered more probable. 



Some 150 modifications on what, from a comparison of the existing forms, we gather to 

 have been the primitive type, are described, and most of those, the original specimens of which 

 are in the National Museum, have been illustrated so as to show the two chief structural 

 characters, the method of growth and the structure of the calicle. The possibilities of varia- 

 tion in each of these two characters, taken alone, are very great, but when there is also colony 

 formation the variability becomes extremely complex. It is one of the more important results of 

 this treatise to have shown that there exists some close interdependence between calicle-forms 

 and growth-forms. Indeed some of the rales of this interdependence have been discovered. 

 For instance, we now know why the calicles at the sides of stocks are always shallower than 

 those in the centre : it is not, as many suggested, a question of age, but is due to this inter- 

 dependence between calicle-form and growth-form. The shallower calicles are, in fact, those 

 produced by the thin expanding or creeping edges of a colony, and hence resemble those 

 typical of explanate stocks. 



* The work is primarily a descriptive catalogue of the representatives of the genus, both recent 

 and fossil, which are preserved in the British Museum of Natural History. In addition, specimens 

 from Cambridge, from Paris, from Leyden and from Rome have been examined at various times. It 

 is to be regretted that all the available material stored in the Museums of Europe could not be 

 brought together for close comparative study. Had that been possible, the results might have been 

 different. 



