APPENDIX 327 



their own negative conclusions in a matter of so 

 much difficulty, and requiring so much knowledge 

 of organic structures in various states of minerali- 

 zation. For myself, after working fifty years at the 

 microscopic examination of fossils and organic rocks, 

 I feel more strongly than ever the uncertainties and 

 liabilities to error which beset such inquiries. 



As an illustration in the case of Eozoon : since 

 the publication of my memoir of 1888, which I had 

 intended to be final and exhaustive as to the main 

 points in so far as I am concerned, I have had 

 occasion to have prepared and to examine about 

 200 slices of Eozoon from new material ; and 

 while most of these have either failed to show the 

 minute structures or have presented nothing new, a 

 few have exhibited certain parts in altogether un- 

 expected perfection, and have shown a prevalence 

 of injection of the canal system by dolomite not 

 previously suspected. I have also observed that 

 unsuitable modes of preparation, notably some of 

 those employed in the preparation of ordinary 

 petrological slices, may fail to disclose organic struc- 

 tures in crystalline limestones when actually present. 

 Since that publication also, the discoveries of Mr. 

 Matthew in the Laurentian of New Brunswick, and 



