FORMATION OF THE SKELETON IN THE MADREPORARIA. 475 



Heider had deciphered this structure iu 1881. Full references 

 to the papers of von Heider and Koch are made in my work 

 (I.e., pp. 91 — 97). Vou Heider made a special study of the 

 soft parts, and observed here and there certain cells iu whose 

 organic contents small groups of calcareous fibres were 

 included, and the nuclei were either shrunken or vanished. 

 To these cells he gave the name of " calicoblasts," and thought 

 they occurred in the mesoderm, but must, in some way, 

 accumulate to build the corallum. As I explained in my 

 paper, Heider's surmise was that the individual skeletal parts 

 in the Madreporaria were formed in a manner analogous with 

 the skeleton of Alcyonarians, but that in the former the 

 calicoblasts produced a solid structure at the outer limit of 

 the mesoderm, whereas the analogous cells in the Alcyonarian 

 polyp formed calcareous spicules, which remained isolated 

 throughout the whole life of the polyp (1. c, p. 93, and cf. 

 Heider, " Korallenstudien," 1886). Heider admitted he could 

 not trace the connection between the groups of fibres as he 

 observed them in cells of the embryonic skeletal disc, and the 

 various complex structures of the mature skeleton. 



Subsequent observers said that the cells referred to by 

 von Heider were components of the ectodermal tissue, and 

 that they never contained inorganic material as he depicted ; 

 that the calcareous material of the corallum was originally of 

 the nature of a secretion thrown out by the cells of the ecto- 

 derm (ref. Ogilvie, 1896, I.e., pp. 101-2). 



This was the position when my work was published by the 

 Royal Society of London, and I there demonstrated that the 

 whole corallum was composed of a series of calcareous 

 lamellce, each of which was primarily an organic tissue com- 

 prising innumerable minute cellular parts, in each of which 

 la}'^ a group of calcareous fibres. As these parts corresponded 

 in appearance to the ''calicoblast " described by von Heider, 

 I applied this term and wrote : "Each lamina (average 

 width '003 to '005 millim.) is a deposit of calico- 

 blasts, the wavy outline corresponding to origin- 

 ally separate cells" (l.c.,p. 123; pp.114 — 117, etc.). 



