1895.] Study of Madreporarian Types of Corals. 



9 



III. "On the Variable Stars of the S Cephei Class." By J. 

 Norman Lockyer, C.B., F.R.S. Received November 9, 

 1895. 



[Publication deferred.] 



IV. " Microscopic and Systematic Study of Madreporarian 

 Types of Corals." By Maria M. Ogilvie, D.Sc. Commu- 

 nicated by Sir Archibald Geikie, F.R.S. Received 

 July 24, 1895. 



(Abstract.) 



In the first part of this paper the author gives the results of her 

 microscopic investigations on the structure of the skeleton in a 

 number of typical Madreporaria. 



Detailed microscopic study of the surface of the septum showed 

 small scales lying above and against one another somewhat like 

 the slates of a roof, and consisting solely of fine, parallel-placed, 

 or diverging, aragonite fibres. Besides these calcareous scales, ecto- 

 dermal cells (calicoblasts) could still be observed in several cases, 

 attached to the surfaces of septa in fresh specimens. Heider and 

 one or two other authors have already mentioned the frequent occur- 

 rence of organic polypal remnants on skeletal surfaces. 



The scales observed by the author were found to agree precisely in 

 shape ar.c. bize with the calicoblasts, and to show various transitional 

 stages from the organic cell to the calcified. It follows from this 

 that the skeleton of Madreporaria takes its origin from an actual 

 calcification of the calicoblasts, and not, as Koch thought, by a secre- 

 tion laid down outside the cells. The author found further that the 

 calcareous scales were arranged in extremely thin lameHse, and that 

 the fibro- crystalline deposit was similarly oriented in successive 

 lamella?. 



The stages in the process of skeleton building may be thus gener- 

 ally stated : — 



(1) Calcareous deposit is laid down within individual calicoblasts 

 of the ectoderm. At the same time new ectodermal cells are formed 

 next the mesogloea, and these which are undergoing calcification 

 become loose external layers of partly calcareous, partly organic 

 tissue. 



(2) Fibro -crystalline groups of aragonite are built up in the indi- 

 vidual cells, and the cell- walls shrivel. Thus a connected calcareous 

 lamella is formed, which is ultimately incorporated with the 

 -skeleton. 



