523 



(" intermediate skeleton"), can only be exhibited with Collins' "gradu- 

 ating diaphragm." " Now these parts, when subjected to decalcification, 

 show no trace of canal system ; so that it is obvious, both from their 

 optical, and from their chemical reactions, that the substance filling the 

 canals must have been carbonate of time"* Another section which Dr. 

 Carpenter has obligingly presented us with is, in some places, crowded 

 with " forms :" some are quite colourless and transparent, and cannot 

 be seen under full light, agreeing thus far with the above descrip- 

 tion. The colourless examples have been distinguished by Dr. Carpenter 

 himself, who has drawn a circle in ink around them. One of the cir- 

 cles contains the beautiful case, represented in Figure 1 1 (PI. XLIY.) as 

 seen magnified 210 diameters, under Webster's condenser, with graduat- 

 ing diaphragms. The " forms" are enclosed in transparent calcite, affected 

 with both rhombohedral and macrodiagonal cleavage. Now rises an 

 important question : — If these " forms " consist of transparent " car- 

 bonate of lime" — why do they, as is invariably the case with them 

 and others in the section, present no traces of the cleavage which so 

 eminently distinguishes the calcite ? Where the " forms" remain covered 

 with, or enclosed in, the calcite, the cleavage lines of this mineral pass 

 over them (as shown at one end of the long cylindrical body in the 

 figure) ; which might mislead some into the idea that the " forms" possess 

 the same crystalline structure as their matrix : but in no instance, where 

 they are uncovered, have we observed the least appearance of any 

 divisional structure in their component substance. From these con- 

 siderations, it may be well imagined that when we partially decalci- 

 fied the section — that is, dissolved the calcite down to only a slight 

 depth, so as not to allow the " forms" to drop out — we were not sur- 

 prised to find them still remaining. Those that are represented in the 

 figure were standing out above the remaining calcite, and as clear as 

 the purest glass. 



The account lately given by Dr. Carpenter, and published with the 

 knowledge of our experiment and observations, affords no further light 

 on this question. " The larger branches" of the " canal system," it is 

 now stated, " were infiltrated with serpentine, and the middle branches 

 with sulphide of iron, while the smallest branches were filled with 

 carbonate of lime, of the same nature" — " of the same crystalline charac- 

 ter" — " as the matrix."f Is cleavage referred to in the last part of this 

 quotation ?J If so, it may belong to the calcite overlying the " canals," 

 as is certainly the case in our specimen. 



It has often been mentioned that " canals" have been seen contain- 

 ing a " yellowish-brown coloration," or " black matter" — a circumstance 



* " Quarterly Journal of Geological Society," vol. xxiii., p. 264. 



f " Quarterly Journal of Geological Society," No. 98, May, 1869, pp. 117, 118. 



% We are glad to gain any additional information from our opponents on the nature 

 of the " branches filled with carbonate of lime," and their enclosing matrix ; but no- 

 thing of the kind appears in the above and latest published account of them. Dr. Car- 

 penter makes some allusion to the " cleavage planes" we have referred to — in such a 

 way, however, that it could be turned not only against " Eozoon," but against himself. 



