Page:Popular Science Monthly Volume 10.djvu/275

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261
THE EARLIER FORMS OF LIFE.

and enormous aquatic growth of algæ, coccoliths, nullipores, and corallines? If we grant that the parasitic fungi could not exist for want of their proper organic food of higher organization, there are still enough forms remaining to take their place, and thus afford us a symmetrical development of all the phases of vegetable growth in the enormous periods when the simplest organic structures ruled the world.

Evidences of Animal Life.—It has been argued by high authority that the existence of carbonate and phosphate of lime suggests the presence of animal life in the Laurentian seas, because at the present day these mineral substances are principally derived from organic secretions. The graphite may also have been partly of animal derivation. There is as much carbon in the Laurentian as in the Paleozoic Carboniferous. But these indications need not be dwelt upon, since recent discoveries have brought to light the actual relics of protozoans preserved in stones of Laurentian age. These are so convincing that the discussion of probabilities derived from rocks of supposed organic origin need not be dwelt upon. The organism has the name Eozoön Canadense, the dawn-animal, inhabiting the Canadian district.

Several names are connected with the discovery of this Eozoön from Ontario and elsewhere. Dr. Wilson, of Perth, sent specimens of it many years since to Sir William E. Logan, Director of Canadian Geological Survey, in which Dr. Sterry Hunt found a new hydrous silicate, which he called Loganite. In 1858 J. McMullen brought specimens which reminded Logan of the Stromatopora of the Silurian. They were examined by various scientists, and in 1865 a composite paper upon the geology, paleontology, and mineralogy of the fossil appeared in the journal of the Geological Society of London, prepared by Messrs. Logan, Dawson, Carpenter, and Hunt. Soon after Vennor discovered other specimens in the Montalban of Tudor, Ontario; Gümbel recognized it in both the Laurentian and Huronian in Bavaria; Bicknell and Burbank discovered it in Laurentian limestones at Newbury and Chelmsford, Massachusetts; and Edwards described it from the Adirondacks in New York. Scientists have not universally accepted the genuineness of this fossil. I will endeavor to present a brief sketch of the nature of the organism before stating their objections.

This animal structure belongs to the subkingdom Protozoa, a unique and inferior group of organisms. These animals are distinguished by possessing no alimentary cavity, or, if a stomach be present, it is not bounded by any walls. The three divisions, using the classification adopted by Dawson, are: the Rhizopods, Sponges, and Infusoria. The first is the lowest, including all the sarcodous animals whose only external organs are pseudopodia. The rhizopods are divided into the Reticularia or Foraminifera, possessing thread-