548 Sir W. Dmcson — The Animal Nature of Eozobn. 



however, that no microscopist who has seen both, under proper 

 conditions of preservation and study, could confound them. The 

 fibres of chrysotile are closely appressed parallel prisms, with the 

 optical properties of serpentine. The best preserved specimens of 

 the " proper wall " contain no serpentine, but are composed of 

 calcite with extremely minute parallel cylinders of dolomite about 

 five to ten microms. in diameter, and separated by spaces greater 

 than their own diameter (see my comparative figure, " Dawn of 

 Life," p. 106 ; also Figs. 5, 6). In the rare cases where the cylinders 

 are filled with serpentine they are, of course, still more distinct and 

 beautiful. At the same time I do not doubt that observers who 

 have not seen the true tubulation may have been misled by chryso- 

 tile veins when these fringe the laminas. Mobius, for instance, 

 figures the true and false structure as if they were the same. 



Protest should here be made against that mode of treating ancient 

 fossils which regards the most obscure or defaced specimens as 

 typical, and those better preserved as mere accidents of mineral 

 structure. In Tertiary Nummulites injected with glauconite, it is 

 rare to find the tubuli perfectly filled, except in tufts here and there, 

 yet no one doubts that these patches represent a continuous structure. 



I have remarked on previous occasions that the calcite constituting 

 the lamina3 of Eozoon often has a minutely granular appearance, 

 different from that of the surrounding limestone. This is, I pre- 

 sume, the " dusty " appearance referred to by Dr. Bonney. Under 

 a high power it resolves itself into extremely minute dots or flocculi, 

 somewhat uniformly diffused. Whether these dots are particles of 

 carbon, iron, apatite, or siliceous matter, or the remains of a porous 

 structure, I do not know ; but similar appearances occur in the 

 calcareous fossils contained in altered limestones of later date. 

 Wherever ihej occur in crystalline limestones supposed to be organic, 

 the microscopist should examine these with care. I have sometimes 

 by this appearance detected fragments of Eozoon which afterward 

 revealed their canals. 



I have not space here to notice late observations on ArchEeospherinse 

 and other objects supposed to be organic found in pre-Cambrian 

 rocks in Canada and in Europe. They afford, however, to some 

 extent, corroborative evidence in favour of Eozoon. 



Supposing a probability to be established of the animal nature of 

 Eozoon, we should naturally expect to detect links of connection 

 between it and fossils known to us in the succeeding geological 

 formations. We have, however, here to make allowance for the 

 probability that an organism so very ancient may differ materially 

 from any of its successoi's, and may probably be a synthetic or 

 generalized type, or present embryonic characters. Analogy might 

 also justify the supposition that it might be represented in later 

 times by smaller as well as more specialized forms. In this con- 

 nection also, the probable warmth and shallowness of the Laurentian 

 ocean, and its abundance in calcium carbonate and in carbonaceous 

 matter, probably organized, should be taken into account. ]t should 

 also be noted that the formations next in ascending order are of 



