Fig. 59.—Figures of various Structures and States of Preservation.
Fig. 1.—Portion of two laminæ and intervening serpentine, with chrysotile vein. (a) Proper wall tubulated. (b) Intermediate skeleton, with large canals. (c) Openings of small chamberlets filled with serpentine. (s) Serpentine filling chamber. (s¹) Vein of chrysotile, showing its difference from the proper wall.
Fig. 2.—Junction of a canal and the proper wall. Lettering as in Fig. 1.
Fig. 3.—Proper wall shifted by a fault, and more recent chrysotile vein not faulted. Lettering as in Fig. 1.
Fig. 4.—Large and small canals filled with dolomite.
Fig. 5.—Abnormally thick portion of intermediate skeleton, with large tubes and small canals filled with dolomite.
On either side of the serpentine band is the nummuline or proper wall, showing under a low power a milky appearance, which, with a higher power, becomes resolved into a tissue of the most beautiful parallel threads, representing the filling of its tubuli. Nothing can be more distinct than the appearances presented by this wall and a chrysotile vein, under every variety of magnifying power and illumination; and all who have had an opportunity of examining my specimens have expressed astonishment that appearances so dissimilar should have been confounded with each other. On the lower side two indentations are seen in the proper wall (c). These are connected with the openings into small subordinate chamberlets, one of which is in part included in the thickness of the slice. At the upper and lower parts of the figure are seen portions of the intermediate skeleton traversed by canals, which in the lower part are very large, though from the analogy of other specimens it is probable that they have in their interstices, and at their branching extremities, minute canaliculi not visible in this slice. [Fig. 2], from the same specimen, shows the termination of one of the canals against the proper wall, its end expanding into a wide disc of sarcode on the surface of the wall, as may be seen in similar structures in modern Foraminifera. In this specimen the canals are beautifully smooth and cylindrical, but they sometimes present a knotted or jointed appearance, especially in specimens decalcified by acids, in which perhaps some erosion has taken place. They are also occasionally fringed with minute crystals, especially in those specimens in which the calcite has been partially replaced with other minerals. [Fig. 3] shows an example of faulting of the proper wall, an appearance not infrequently observed; and it also shows a vein of chrysotile crossing the line of fault, and not itself affected by it—a clear evidence of its posterior origin. [Figs. 4 and 5] are examples of specimens having the canals filled with dolomite, and showing extremely fine canals in the interstices of the others: an appearance observed only in the thicker parts of the skeleton, and when these are very well preserved. These dolomitized portions require some precautions for their observation, either in slices or decalcified specimens, but when properly managed they show the structures in very great perfection. The specimen in [Fig. 5] is from an abnormally thick portion of intermediate skeleton, having unusually thick canals, and referred to in a previous chapter. Such additional peculiarities and specialties might be multiplied to any extent from the numerous prepared specimens now in our collections.
One object which I have in view in thus minutely directing attention to these illustrations, is to show the nature of the misapprehensions which may occur in examining specimens of this kind, and at the same time the certainty which may be attained when proper precautions are taken. I may add that such structures as those referred to are best seen in extremely thin slices, and that the observer must not expect that every specimen will exhibit them equally well. It is only by preparing and examining many specimens that the best results can be obtained. It often happens that one specimen is required to show well one part of the structures, and a different one to show another; and previous to actual trial, it is not easy to say which portion of the structures any particular fragment will show most clearly. This renders it somewhat difficult to supply one's friends with specimens. Really good slices can be prepared only from the best material and by skilled manipulators; imperfect slices may only mislead; and rough specimens may not be properly prepared by persons unaccustomed to the work, or if so prepared, may not turn out satisfactory, or may not be skilfully examined. One slice heated in the grinding may show nothing but cleavage in the calcite layers, while an adjoining one more carefully prepared may show beautiful canals. These difficulties, however, Eozoon shares with other specimens in micro-geology, and I have experienced similar disappointments in the case of fossil wood.
In conclusion of this part of the subject, and referring to the notes appended to this work for some further details, I would express the hope that those who have hitherto opposed the interpretation of Eozoon as organic, and to whose ability and honesty of purpose I willingly bear testimony, will find themselves enabled to acknowledge at least the reasonable probability of that interpretation of these remarkable forms and structures.
THE ORIGIN OF LIFE