160 Mr Matthui, la the Madveporarian Skeleton 



Is the Madveporarian Skeleton an Extraprotoplasmic Secretion 

 of the Polyps ? By G. Matthai, M.A., Emmanuel College, Cam- 

 bridge. (Communicated by Professor Stanley Gardiner.) 



[Read 18 February 1918.] 



In 1881 von Heider (5) suggested that the calcareous skeleton 

 of the Madreporaria is formed by the deposition of carbonate of lime 

 within certain specialised ectodermal cells (calicoblasts*) consti- 

 tuting an outer layer, and repeated this conclusion in a subsequent 

 paper (6). In 1882 von Koch (8) inferred from embryological obser- 

 vations that the skeleton is deposited outside the living tissues, 

 i.e. is extraprotoplasmic in origin. In 1896 Ogilvie (9) supported 

 von Heider's view and argued that, by repeated calcification of 

 "cells" of the calicoblastic layer of ectoderm, successive strata of 

 calcareous " scales " are formed, and slightly modified her opinion 

 in 1906 (10). Fowler (4) had previously accepted von Koch's view. 

 In 1899 Bourne (2), from his studies on the Anthozoan skeleton, 

 supported von Koch's conclusions and entirely disagreed with 

 von Heider and Ogilvie. He further held that, whilst in Heliopora 

 and the Madreporaria the corallum is formed outside the living 

 calicoblastic layer, the spicules of the Alcyonaria are formed within 

 certain ectodermal cells or scleroblasts which either remain in the 

 ectoderm or wander into the mesoglaea (2, p. 506). Following 

 von Koch and Bourne, it is noAv generally believed that the 

 Madreporarian skeleton is an extraprotoplasmic formation and that 

 Alcyonarian spicules are entoplastic products. 



After a ground-down section of an Astrgeid corallite has been 

 slowly decalcified on a slide, somewhat homogeneous organic 

 remains (distinguishable from algal filaments penetrating the 

 skeleton) are left which react to any of the common stains. This 

 is clear indication that the calcareous matter has been deposited 

 in an organic matrix. Bourne regards this matrix as due to the 

 "disintegration of calicoblasts" (2, pp. 520 and 521, fig. 21), 

 assuming that the organic basis was not part of the living calico- 

 blastic ectoderm. His view is that carbonate of lime is secreted 

 by the calicoblastic layer and is passed through its outer border 

 (the " limiting membrane ") into the decaying part outside, exactly 

 as the Alcyonarian spicule is " from its early origin, separated 

 from the protoplasm which elaborated the material necessary for 

 its further growth by a layer of some cuticular material" (2, p. 537), 



* Von Heider's original rendering of this word is chalicoblast, of which the first 

 half, I am informed, is derived from the Greek x'^^'li which in Eomau characters 

 should be spelt clialix. Subsequently, Fowler changed the spelling to calycoblast, 

 and in 1888 both this author and Bourne adopted the present form calicob/ast. 



