196 THE DAWN OF LIFE. 



imperfectly imitative. I may add, that the case is one of the 

 occurrence of a canal structure in forms which on other 

 grounds appear to be organic, while the concretionary forms 

 referred to are produced under diverse conditions, none of them 

 similar to those of which evidence appears in the specimens of 

 Eozoon. With the singular theory of pseudomorphism, by 

 means of which the authors now supplement their previous 

 objections, I leave Dr. Hunt to deal. 



4. With respect to the proper wall and its minute tubulation, 

 the essential error of the authors consists in confounding it 

 with fibrous and acicular crystals, and in maintaining that 

 because the tubuli are sometimes apparently confused and con- 

 fluent they must be inorganic. With regard to the first of these 

 positions, I may repeat what I have stated in former papers — 

 that the true cell-wall presents minute cylindrical processes 

 traversing carbonate of lime, and usually nearly parallel to 

 each other, and often slightly bulbose at the extremity. 

 Fibrous serpentine, on the other hand, appears as angular 

 crystals, closely packed together, while the numerous spicular 

 crystals of silicious minerals which ofter appear in metamorphic 

 limestones, and may be developed by decalcification, appear 

 sa sharp angular needles usually radiating from centres or 

 irregularly disposed. Their own plate (Ophite from Skye, 

 King and Eowney's Paper, Proc. B. J. A., vol. x.), is an 

 eminent example of this ; and whatever the nature of thai; 

 crystals represented, they have no appearance of being tnn 

 tubuli of Eozoon. I have very often shown microscopists and 

 geologists the cell-wall along with veins of chrysotile and 

 coatings of acicular crystals occurring in the same or similar 

 limestones, and they have never failed at once to recognise the 

 diff'erence, especially under high powers. 



I do not deny that the tubulation is often imperfectly pre- 

 served, and that in such cases the casts of the tubuli may 

 appear to be glued together by concretions of mineral matter, 

 or to be broken or imperfect. But this occurs in all fossils, 

 and is familiar to any microscopist examining them. How 

 difficult is it in many cases to detect the minute structure of 

 Nummulites and other fossil Foraminifera P How often does 



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