502 GILBERT 0. BOURNE. 



(loc. cit., p. 102), " I find, however, that Koch, Fowler, and 

 Bourne are wrong in their conception of tlie calicoblast. My 

 investigation of the superficial layers of the skeleton have 

 given the fullest confirmation of Heider's idea, that the calico- 

 blasts were actually converted into calcareous groups of fibres. 

 I hope to show, in the course of this paper, that the fibre- 

 containing calicoblasts which lie next to the ske- 

 leton are shed off, so to speak, from the polyp, new cells 

 taking their place in the ectoderm by cell division. The 

 shed calicoblasts build up successive layers of calcified cells, 

 which hang together at first by their cell- walls, and ultimately, 

 as crystalline changes continue, form the individual laminse of 

 the skeletal structures. The whole Madreporarian skeleton is 

 formed of such laminae ; any apparent variation in microscopic 

 structure is accounted for by some difference in the shape and 

 position, locally, of the ectoderm." The quotation shows that 

 Mrs. Gordon attached great importance to the conception of 

 the formation of the corallura from a number of calcified cells, 

 and she made it the basis of a number of interesting specula- 

 tions concerning the origin of the diflferent types of coral 

 structure which she described. 



On p. 115 of the same work Mrs. Gordon gives an account 

 of the isolated skeletal elements of the Madreporarian 

 corallum. These she discovered to be scale-like structures 

 entirely filled with a bush of minute fibres ; others had granular 

 contents, or partly fibrous, partly granular. The resemblance 

 of these scales to the striated structures described as calico- 

 blasts by von Heider led Mrs. Gordon to seek for proof of the 

 identity of the two. I give Mrs. Gordon's proof in her own 

 words. " It has been frequently mentioned by writers on 

 corals that organic remnants after removal of the polyp may 

 be found on the skeleton. Wherever on the skeleton 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. The contents 

 varied from yellowish organic-cell material to the inorganic 

 fibrous condition. Comparison of my own observations on 



