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 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. 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. 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 chapter for 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. NOTES TO CHAPTER VII. (A.) Objections of Profs. King and Rowney. _Trans. Royal Irish Academy, July, 1869._[AO] [Footnote AO: Reprinted in the _Annals and Magazine of Natural History_, May, 1874.]