478 MARIA M. OGILVIE GORDON. 



patches. Those are doubtless due to irregular disposition of 

 the calicoblasts, as they originally separate from the ecto- 

 dermal poly pal layer" (id., 1. c, p. 1 IG). 



Mr. Duerden's work/ referred to by M. Krempf, brought 

 the first confirmation of my description of the primarily 

 organic nature of the layer external to the ectoderm in 

 which the skeletal elements developed, but Mr. Duerden 

 described it as homogeneous, and thought it took origin from 

 the ectoderm probably by a process of secretion, and that the 

 calcareous groups of fibres which made their appearance 

 must be regarded as '^ ectoplastic " in origin. Against this 

 I wrote as follows : 



"On Mr. Duerden's interpretation, if I understand it 

 aright, we are to believe that the exceedingly particular 

 skeleton arises by a sort of crystallisation in an organic 

 cuticular matrix produced by, but distinct from, the ecto- 

 derm. I still uphold my opinion, supported by remarkable 

 correspondences of measurements, which cannot be mere 

 coincidences, that the individual ectoderm cells or nuclear 

 parts exert a determining individual influence on the origin 

 of the lime-forming skeletal units {= " calicoblasts " in my 

 work) in the cuticular product, which is, after all, a composite 

 product from many ectodermal cells, and persists in retaining 

 its originally particulate character." (' Quart. Journ. Micr. 

 Sci.,' 1905.) 



"Each individual lime-forming part or ' calicoblast' of 

 the skeletal layer derived its origin from an ectoderm cell in 

 virtue of divisional processes, part of the cell layer continuing 

 as ectoderm, part being shed as the layer of calicoblasts " 

 ('Quart. Journ. Micr. Sci.,' vol. 49, pt. 1, Oct., 1905, pp. 207, 

 208). 



M. Krempf now recognises the distinct partitioning of the 

 groups of calcareousfibres by organic straiids,butsaysaltliough 

 these simulate cell-walls in their appearance, the contained 



1 J. E. Duerden, "The Coral Siderastraea radians and its Post-larval 

 Development," Washington, U.S.A., publ. by Carnegie Institution, Dec., 

 1904. 



