PRE-CAMBRIAN PERIOD. Plant Life.—No remains of plants have been observed, although from other circumstances their existence has been inferred. No more difficult problem remains to be solved than the history of the first appearance of life on the globe. Is the Laurentian of North America, with its one known solitary organism, the oldest sedimentary rock existing? is Eozoon canadense the oldest known form of life? Re search up to the present time has not revealed to us one of higher antiquity; neither has it even a truly associated form. No Plant, Protozoon or Annelid, accompanies this still mysterious progenitor of Palaozoic life. The Eozoic or Laurentian gneiss of Britain or Europe, lias not yet yielded a semblance of anything approaching Protozoic affinities, although in the Hebrides, Norway, Sweden, Bo hemia, and Bavaria these rocks have long been recognised. That the Laurentian rocks are not the oldest is manifest; others of infinitely greater age yielded sediment to the Laurentian sea, and pabulum for the sustenance and material for the shelly structure of its supposed only inhabitant; but whether Eozoon had precursors or not, time will probably tell. If any older forms of animal life did exist, they cannot have belonged to much simpler types— “ Naked Protozoa would have left no sign of their existence, ex cept probably minute traces of carbonaceous matter.” Plant life, however, may have preceded Eozoonal, and may thus have accumulated previous stores of organic matter. We have already referred to the occurrence of graphite in the Archaean rocks, and its constituting twenty per cent, of some layers. This is strong evidence that plants of some kind were abundant, though, as suggested by Dr. Sterry Hunt, animal life may have afforded part of the carbonaceous material, and, perhaps, as large a part as vegetable life. The presence of graphite in large deposits occurring both in beds and veins in the Laurentian rocks, clearly determines that its origin and deposition were contemporaneous with the mass or containing rock ; the graphite, again, is associated with calcite, quartz, and ortho clase. It is not improbable that the “ vein graphite ” was introduced as a liquid hydrocarbon. Dr. Sterry Hunt believes it possible that it may have been produced in a state of aqueous solution. 1 In the lower Laurentians the quantity of graphite is enormous ; its origin may have been due to the deoxidation of carbonic acid by living plants. That the graphitic matter of the Laurentian rocks was laid down or accumu lated in beds like coal is improbable, no evidence whatever tending to show that there existed terrestrial vegetation. On the other hand, the hydrocarbon may have been due to diffused bituminous matter closely resembling “ our bituminous shales and bituminous oil-bearing limestones.” Research hitherto has failed to find traces of any organ ism save the Eozoon ; no cryptogam has yet occurred; and we cannot imagine that, if of vegetable origin, the organic matter could have been so completely disintegrated and bituminised prior to being changed into graphite. 1 Hunt, “Report of the Geological Survey of Scotland," 1866.