502 



ME. H. M. BEEKAED ON THE AFFHSTTIES OP 



Now I admit that there is more to be said for this view than I 

 was at first inclined to allow. But the usual argument employed 

 in its favour is not conclusive. We are referred to the black 

 median line which runs through the walls when studied in thin 

 sections under the microscope. It is not necessary to discuss 

 the many different views which have been held in the past as to 

 the real nature of this black line. I need only refer readers, on 

 this point, to the recent work of Miss Ogilvie (I. c. antea), where 

 the history of the subject is reviewed and the matter is fully and, 

 from the existing standpoint, adequately discussed. The black line 

 simply means that this apparently double wall was secreted by a 

 continuous fold of tissue. Similar black lines are invariably 

 found down the middle of septa secreted by ectodermal folds ; 

 hence we should expect them to appear in the walls of calicles 

 which are built up of septa, as explained for Alveopora. 



Pigs. 4 and 5 are drawn by Mr. Percy Highley from sections 

 of the Palaeozoic Favosites gntJilandica and of a recent Alveopora. 

 We find the same black line runniug down the middle of the 

 skeletal framework in both cases. That in the fossil is slightly 

 more pronounced than that in the recent coral, but there is 

 no reason whatever to believe that they were dissimilar in 

 origin. Besides, I have seen it stated somewhere, I think by 

 Miss Ogilvie, that the black streak is usually much more pro- 

 nounced in Palseozoic than in recent corals. 



We are then, I think, fully justified in claiming that in 

 Favosites the perforated calicular walls may have arisen, as in 

 Alveopora, from the meeting and fusion of the septa, and are not 

 the outer walls of separate and distinct polyps. This claim seems 

 to me to find further support when the common epithecal cup, 

 which is known to have contained the young colonies of Favosites, 

 is taken into consideration. Within such a cup, the fission or 

 gemmation of the polyps for the formation of such a compact 

 stock as that of Favosites could, it would seem, hardly proceed 

 in any other way than that which we have described for Alveo- 

 pora. Further, a study of the section of Favosites (fig. 4) shows 

 this same black line not contained only in the walls but running 

 up the septal spines *, as we should expect it to do on the 

 assumption that the walls are septal structures, while it is hardly 

 consistent with the usual explanation that the black line repre- 



* Cf. also v. Koch's section of Alveopora, in which the same is shown. 



