38 Principal J. W. Dawson on Eozoon canadense. 



the best answers to what may be called the " pseudomorphic " 

 objections to Eozoon. 



It may, however, be useful to notice the few points raised 

 in the " Supplementary Note," as these refer to my recent 

 paper in the Journal of the Geological Society. (1) In this, 

 as well as at page 368, your correspondents appear to object 

 to the canals filled with Dolomite as exceptional, though it is 

 not easy to understand the meaning of the statement by which 

 they endeavom- to reconcile this Dolomite-filling with their 

 theory of the foimation of the canal-system by the " erosion 

 or decretion of portions of serpentine." I may explain that 

 this kind of filling is not at all rare in the specimens from 

 Petite Nation. I have now in my cabinet at least thirty pre- 

 parations of this kind, decalcified to show the canals, besides 

 others as slices, and many w^hicli I have prepared but have not 

 preserved. Of course I could not figure more than a few ; 

 but I did not intend to convey the impression that this appear- 

 ance is ver)^ rare at the locality in question. (2) They absurdly, 

 perhaps in jest, claim me as a disciple of their theory of pseudo- 

 morphism, because I have described a specimen, the only one 

 I have yet met with, in which the skeleton is in part " re- 

 placed "with serpentine; but such replacement is of course 

 no more pseudomorphism than tliat which occurs when corals, 

 shells, or wood are replaced with quartz or pyrite. (3) As to 

 the " chevi'on arrangement," I think I have stated clearly 

 enough that this is not in accordance with my observation ; 

 and I cited Mr. Weston as one who has prepared and examined 

 more specimens than any other person. Both of us have the 

 impression that the tubuli of the cell-wall are somewhat uni- 

 form in length, and the cell-wall itself parallel-sided, except 

 where affected by flexures and microscopic faults. But on 

 this subject your correspondents may, I have no doubt, obtain 

 Mr. Weston's direct testimony, if they desire it. It is no 

 doubt true that decalcified specimens of the cell-wall often 

 have a ragged and imperfect appearance ; but this is due to the 

 great difficulty of preserving such delicate fibres intact ; and 

 this is a sufficient reason for my pi'cference of very thin slices 

 as the best means of exhibiting this structiue. I may add 

 that I think no one who has seen under polarized light such 

 specimens as those figured in plate viii. figs. 1 to 3 of ' The 

 Dawn of Life,' or plate x. fig. 3 of my paper in the Journal 

 of the Geological Society, could for a moment doubt the funda- 

 mental diiFerence of the proper wall and chrysotile veins. 



May 27, 1876. J. W. D. 



