3. I took occaHion to ineution certain errors of Prof. Moebius, 

 due* to his limited inforrautiou on tlic subject of which he treats. 

 He admits two of these, wliich were particularly pointed out, but 

 taunts me with not producing others. This, however, would not 

 have been difficult had I been disposed to enter in detail into a 

 task so ungracious. Another example may be taken from his 

 plate XXXV, in which he represents together, and obviously for 

 comparison, portions of the pores or tubuli of the modern Pnly- 

 tirnia. and an imperfect fragment of the proper wall of Eozoon. 

 and this more especially, as appears in the text, to show the 

 comparative fineness of the latter. But the specimen of Eozoon 

 is magnified only 75 diameters, while that of Polytrema is mag- 

 nified 200 diameters, or in the prnportioii of oH'i.') to 40,000. 

 Again he has affirmed and repeats in his reply tint the casts 

 of the canal systems of Eo::oon do not present cylindrical forms 

 but are ''flat and uvr^'f^fO' branched stalk-like bodies." If they 

 appeared .so to him, he must have possessed most exceptional 

 specimens. Some canals, especially the larger, no doubt have 

 flattened ibrms, particularly at their points of bifurcation ; but 

 this is comparatively rare, more especially in the vastly nu- 

 merous minute canals which are more frequently filled with dolo- 

 mite than with serpentine. T have indeed been able to detect 

 only a few out of very numerous specimens in which the majority 

 of the casts of canals are not approximately round in cross .sec- 

 tion, even in the case of the larger canals. It is a <(uestion also 

 if some flattening may not be due to pressure , and there are flat 

 stolon-like tubes which can scarcely be called canals.^ 



It occurs to me here to remark that Moebius seems to have 

 overlooked the extremely fine canals injected with Dolomite that 

 fill the upper and thinner calcite walls of the better preserved 

 specimens, and which in the thinner walls are nearly as fine as 

 the tubuli of the j)roper wall, into which in many cases they 

 almost insensibly pass where these last are themselves filled with 

 dolomite. Possibly these structures iiave not been present in 

 his specimens, or may have been destroyed or rendered invisible 

 by his methods of prejiaration, and if so this would account for 



• Tlie forms of the canals are jjorliaps best seen in (lecaleifiert 

 siu'cimens ; l>nt Mr. Weston, who has done so mneli toward this in- 

 vesti.gation, has managed to eut slices so aoturately at right anghis 

 to th«! general (course of groups of canals, as to show tluir round cross 

 sections with great distiu'tness. 



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