MORPHOLOGY OF THE CORAL SKELETON. 35 



research into the hard parts of corals, should receive special mention. This 

 is Pratz's memoir, entitled Ueber die verwandschaftlichen Beziehungen 

 einiger Korallengattungen mit hauptsachlicher Berlicksichtigung ihrer 

 Septalstructiu'/ 



ORIGIN OF THE CALCAREOUS DEPOSIT. 



The first question concerning the skeleton of corals that engages one's 

 attention is the origin of the calcareous deposit. Von Koch, in Ueber die 

 Entwickeluno- des Kalkskeletes von A.steroides calvcularis und dessen mor- 

 phologischer Bedeutuug, first showed that the calcareous substance is origi- 

 nated by the ectodermal layer. He also considered the skeleton to be secre- 

 ted by the ectoderm and not formed by the calcification of it. The latter 

 question has been much debated. Von Heider has maintained that the 

 skeleton originates by an actual calcification of the cells,^ and believes that 

 he has recognized calcareous granules within the cell walls. Bourne doul^ts 

 the accuracy of this observation and gives another interpretation of the 

 phenomena.^ Miss Ogilvie has strongly supported the view of von Heider. 

 She has a rather lengthy discussion of the subject in her description of the 

 septum of Galaxea.* Tht) following extract shows the character of the ulti- 

 mate proof given by her: 



It has been frequently mentioned by writers on corals tliat organic remnants 

 after removal of the polyp, may be fouiid on tbe skeleton. Wherever on the surface 

 I found such remnants, they consisted of calicoblasts which showed, in shape, size, and 

 contents, the varieties already drawn by Von Heider. The cells were round, or obovate, 

 Tbe contents varied from yellowish organic cell material to the inorganic fibrous condi- 

 tion. Comparison of my own observations on several corals with the figures given by 

 Von Heider, left uo doubt that the isolated skeletal element was a calcified calicoblast cell. 



The italics are Miss Ogilvie's. 



Further on,° in speaking of the dark bands of the growth lamella^ of 

 the septa, she says: 



The highest magnifying power never displays any structure in the case of points 

 or bands that appear dark, but only shows a general amorphous substance, which I van 

 only regard as the carbonized residue of the originally unchanged organic parts of the 

 calicoblasts. 



' Palii'ontographica, Vol. XXIX. 



= Sitzung8b. K. Akad. Wiss., Wien, Vol. LXXXIV, Sect. I, Dec. No., 1881, pp. 652,653, 658. Von 

 Heider, in this paper, names the skeletou-forming cells calicoblasts. 

 ^ Quart. Jour. Microsc. Sci., Aug., 1897, pp. 25, 26. 



< Microscopic and Systematic Study of Madreporarian Types of Corals, pp. 114 to 117. 

 •'Ibid., p. 127. 



