CONNECTING AND MISSING LINKS
Our fossil record begins with the dawning of the Palaeozoic era, some 500,000,000 years ago, but the date of the origin of life was vastly more remote, for when the fossil record actually begins not only is life fully manifest, but the numerous animal stocks that constitute its invertebrate division are already well established. These earliest known animals are far more diverse and complex than the most primitive imaginable organisms, some of which yet exist—such as the slime molds and the bacteria described as prototrophic (literally "first feeding"). Thus the missing links in the early evolution of animal life constitute for millions of years the entire chain. There is, however, no doubt in the scientific mind that the oldest known fossils imply, with the assurance of certainty, a long antecedent evolution, much of which, in spite of the fact that palaeontology is silent, can be deduced from the sister sciences of comparative anatomy and embryology. The reason the record anterior to this time is blank is because of the nature of the organisms themselves. Composed as they were largely of soft parts with no limy skeletons, or shells, they apparently left little to be preserved in the rocks of ancient time. Consequently, save for certain remarkable impressions, yet to be described, little of the actual nature of these ancestral types is known, except by inference, until they had established what has been called the lime-secreting habit, which was formed by animals in mid-Cambrian time, by plants somewhat earlier. True, there are masses of limestone, iron ore, and graphite in the pre-Palaeozoic rocks, all of which are regarded as largely of organic origin, but, although their presence is indirect evidence of the existence of organisms in this remote time, it reveals nothing of their nature.
One notable exception lies on the flank of Mount Wapiti, near Field, in British Columbia, where, in a small area of
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