Page:Popular Science Monthly Volume 10.djvu/281

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267
THE EARLIER FORMS OF LIFE.

and only silica remains, the rhomboidal pieces being the only remnants of the original structure. The Eozoön has not been so completely fossilized as in the example of coniferous wood. The cell-wall and supplementary skeleton still retain much of the original lime, while the animal part has been entirely replaced by serpentine or some other mineral. Subsequent pressure or desiocation has produced cracks in the mass, which have been filled with an asbestus-like mineral of silky lustre, and this has sometimes been confounded with some part of the animal by objectors. a l

PSM V10 D281 Magnified eozoon.jpg
Fig. 5.—Canals of Eozoön, highly magnified. Fig. 6.—Coniferous Wood, illustrating Fossilization.
a, Partially mineralized, the white spaces being silica, the black vegetable matter; b. Vegetable matter removed by decomposition, leaving outline of the forms of the original pores.

Few special subjects have been so carefully studied as the genuineness of Eozoön. The treatises of Logan, Dawson, Carpenter, and Hunt, admirably set forth every possible phase of geological position, intimate zoological structure and affinity, mineral character both original and derived, and the conditions of origination. The elaborate papers of the objectors, Messrs. King, Rowney, Carter, Burbank, and others, show what the weaker positions are, and have enabled the advocates to satisfactorily fortify the less defensible points of their arguments. Every new discovery seems to aid the defenders, while the philosophy of evolution is in harmony with the existence of a long Eozoöic age where the predominant life is scarcely elevated above the working of crystalline forces.

Huronian Life.—Gümbel has described a species of Eozoön from the supposed Huronian rocks of Bavaria. In this country Billings has mentioned the occurrence of an Aspidella and Arenicolites from a series of Newfoundland rocks called "Intermediate," most probably of this age. The Aspidella bears some resemblance to the limpet-shell or Patella, while it may have been some variety of crustacean. The Arenicolites is a petrified worm-burrow.

But the specimens of greatest interest are those brought to light the present year by Mr. George W. Hawes from the Huronian of