No wonder then that geologists have long and earnestly groped in the rocky archives of the earth in search of some record of this patriarch of the animal kingdom. But after long and patient research, there still remained a large residuum of the oldest rocks, destitute of all traces of living beings, and designated by the hopeless name "Azoic,"--the formations destitute of remains of life, the stony records of a lifeless world. So the matter remained till the Laurentian rocks of Canada, lying at the base of these old Azoic formations, afforded forms believed to be of organic origin. The discovery was hailed with enthusiasm by those who had been prepared by previous study to receive it. It was regarded with feeble and not very intelligent faith by many more, and was met with half-concealed or open scepticism by others. It produced a copious crop of descriptive and controversial literature, but for the most part technical, and confined to scientific transactions and periodicals, read by very few except specialists. Thus, few even of geological and biological students have clear ideas of the real nature and mode of occurrence of these ancient organisms, and of their relations to better known forms of life; while the crudest and most inaccurate ideas have been current in lectures and popular books, and even in text-books, although to the minds of those really acquainted with the facts, all the disputed points have long ago been satisfactorily settled, and the true nature and affinities of Eozoon are distinctly and satisfactorily understood. This state of things has long ceased to be desirable in the interests of science, since the settlement of the questions raised is in the highest degree important to the history of life. We cannot, it is true, affirm that Eozoon is in reality the long sought prototype of animal existence; but it is for us at present the last organic foothold, on which we can poise ourselves, that we may look back into the abyss of the infinite past, and forward to the long and varied progress of life in geological time. Its consideration, therefore, is certain, if properly entered into, to be fruitful of interesting and valuable thought, and to form the best possible introduction to the history of life in connection with geology.