510 MR. H. M. BERNARD ON THE AEEINITIES OF 



in the diagram, we note that wherever a true theca is formed, the 

 epitheca tends to be pushed more and more into the background, 

 so as to become quite vestigial, and that this is the case in the 

 great bulk of the recent Madreporaria. It is further to be noted 

 that the possibilities of colony-formation are enormously in- 

 creased in the more purely septate skeletons than they ever 

 could have been in tbe primitive epithecate stage. The height 

 and development, number and character of the septa, the position 

 and character of the uniting tissue to which, when not dissepi- 

 mental, I give the general term " synapticular," which gives rise 

 to the theca, may vary considerably ; and every slight difference is 

 then magnified by its indefinite multiplication in colooiy-formation. 

 Further, it is fairly obvious that the forms with synapticular thecse 

 would show a far richer development than would those with the 

 less plastic dissepimental thecse. 



Budding. — The remark made at the beginning of this paper 

 that certainly some forms of " intracalicular " gemmation may 

 be true cases of lateral gemmation is made clear by the diagrams. 

 If a lateral bud arises (as in fig. 6) above the epithecal rim which 

 bends out beneath it, the dividing wall between parent and bud 

 is naturally supplied by the septal spines. We have every right 

 to assume that this is what actually takes place in Alveopora : 

 certainly the rim of the epitheca can be seen to bend out, and on 

 the other hand we know from published figures that the polyps 

 rise high above their skeletons. In those cases in Mhich the 

 epitheca in further growth encases the parent and the bud 

 separately, we have colony-formation of purely epithecate 

 skeletons. A very primitive colony-formation of this character 

 has been minutely and iostructively described by Beecher *. 



Passing, then, from the budding of an epithecate coral which 

 may produce either an epithecate colony, as in the example cited, 

 or a colony in which the epitheca of the parent polyp becomes a 

 common epitheca to tbe whole colony, the skeletons of individuals 

 being septate but not thecate — e. g. Alveopora, and apparently 

 Favosifes, — we come to the budding of polyps with purely septate 

 skeletons. We note from the diagrams that the budding re- 

 mains the same, viz. lateral gemmation; but the form of the 

 skeleton has changed, the rising up of the septa, with their 

 synapticulse for mutual support, gives a new groundwork on 



* Trans. Conn. Acad. Toi. viii. p. 207, 1891, pis. ix.-xiii. See also Postscript, 

 infra, p. 515. 



