LIME-FORMING LAYER OF MADREPORARIAN POLYP. 207 
“When of sufficient thickness to have contained skeletal 
fibres, now dissolved away, this membrane appears fibrous, 
but immediately bordering the calicoblast layer” (by which 
he means the ectoderm) ‘‘it is homogeneous ” (Duerden, l. c., 
p. 34). 
Seeing that the term “ calicoblast”’ means “ lime-forming,” 
why not apply it to the membrane which, in Mr. Duerden’s 
own interpretation is a lime-forming layer? Why apply the 
term “calicoblast”’ to the persistent ectoderm, which is not 
directly lime-forming, as was erroneously supposed by those 
who made the precedent? Moreover, in common with me, 
Mr. Duerden considers this lime-forming layer to be sepa- 
rated time after time by the ectoderm, and to be originally 
organic, secondarily inorganic. Had he used the same 
terminology as I did, designating as ‘‘calicoblasts” the 
skeletal unit-elements (partially organic, partially fibrous) 
present in the layer, and the whole layer a “layer” or 
“lamella of calicoblasts,” the similarity of our results 
would have been self-evident, the important feature being 
that the ectoderm does not separate out calcareous 
matter, but organic matter, within which the 
crystals develop. 
The point of difference between Mr. Duerden’s results and 
mine is one of histological detail. From the remarkable 
coincidence in size between the cells of tne persistent ecto- 
derm and the calicoblast unit-element in the apposed skeletal 
or lime-forming layer, I drew the conclusion (aut., pp. 115, 
117, 124, 125, 217, etc.) that the change from the organic to 
the inorganic state went on in individual cellular parts of the 
lime-forming layer, and that each individual lime-forming 
part or “ calicoblast ” of the 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. 
Mr. Duerden finds the lime-forming layer homogeneous in 
character, without cell limitations, and, as I made no further 
investigation of the subject, I willingly accept Mr, Duerden’s 
