PROOFS OF EVOLUTION. 
31 
VI. 
PROOFS FROM EMBRYOLOGY. 
Perhaps the most striking evidence of the 
truth of Evolution, is found in the study of 
Embryology, which is the science of the embryonic 
cell. Three great stages of growth may here be 
noted, the cell, the individual, and the tribe. 
That all organic life has been evolved from 
primordial germ-cells during countless ages, is 
now the firm position of Science. Even the 
method and laws of growth have been clearly 
outlined. The microscopic germ-cell, when first 
stirred by the energy of life, subdivides, producing 
two primary germ-layers,—by fission again devel¬ 
oping four secondary germ-layers, and so on. 
These new cells do not entirely separate, but 
remain in contact. From the continual aggrega¬ 
tion of cell-forms, all the organs and parts of the 
body are developed. When an egg is formed by a 
multiplicity of cells, it separates into three distinct 
layers, called the ecto-blast, the endo-blast, and 
the meso-blast, from which are developed by differ¬ 
entiation the three great life-centres, namely, the 
