Fistulipora iucrustans, P/^^77. (F. minor, J/' Coy). 243 



the peculiarity that exists in the lighter sclerenchyma-layer 

 (although they do not call it such) that rests on the folds or 

 raised lips of the autopores in F. incrustans, and state 

 (j). 498), " This lighter portion consists of crystalline calcite 

 of a similar character to that of the matrix or infilling of the 

 cells, though very slightly darker, while the remaining portion 

 of the cell-wall and the walls of the mesopores are composed 

 of a dense, granular, opaque calcite." 



It seems to be evident from this statement that their sec- 

 tions did not show any trace of foramina or pores in the calcite 

 that forms the thickened lips of the cells ; but they are agreed 

 that the sclerenchyma-layer, which they term a " crystalline 

 calcite," was organically formed, for they further state, " This 

 difference in the mineral composition in the two parts of the 

 cell-wall must certainly have originated in the living tissues 

 of the organism, because the same phenomenon is met with in 

 species from such widely separated localities as Canada and 

 Westphalia." 



I do not think that any evidence can be clearer than that 

 such was the case, although the further evidence of organic 

 structure in the form of minute perforations, such as those I 

 have referred to, seems to have been absent in their specimens. 



When the sclerenchyma-layers are examined in vertical 

 sections under the microscope it is seen that the foramina or 

 tubes pass upwards through the deposit nearly at right angles 

 to its growth, the only radiation seen in the structure being 

 due to the curving of the sclerenchyma over and around the 

 convex cells of the mesopores. In the thickened layer that is 

 seen resting on the folds of the depressed autopores in the 

 younger stages of growth the foramina also pass through 

 the deposit nearly at right angles to the tubes on which 

 it rests. The foramina or tubes in the sclerenchyma often 

 give the layers a fibrous or brush-like structure, which, 

 when viewed in vertical sections, appears as fine in the tex- 

 ture as very fine velvet. 



In tangential sections the foramina in finely preserved 

 specimens are seen as very minute pores. Whether any of 

 these pass through the true cell-walls, either in the autopores 

 or mesopores, is a point on which I have not obtained clear 

 evidence as yet; but I am inclined to think that they do, 

 and this is also the opinion of Mr. Ulrich, from an examina- 

 tion of American specimens. In some of my sections I find 

 a peculiar and minutely broken-up condition of the denser 

 portion of the cell- wall that presents the appearance of having, 

 as it were, been perforated by tubes ; but as this is not 

 clearly seen in every section, I am doubtful whether such a 



