CHAPTER IV. 



THE RECORD FROM FOSSILS. 



WE have thus far traced the history of animals 

 through the unicellular stage to the Gastraea type, 

 and we have seen that this Gastraea probably diverged 

 rapidly, by various modifications in the shape and 

 structure of its body, into different sub-kingdoms. 

 Thus far our evidence has been only sufficient to 

 indicate such general facts with no details. Embry- 

 ology, with the assistance of comparative anatomy, 

 has told us all that we know of this early history of 

 living things, and these two sources of evidence, as 

 already pointed out, can give no details. Still it is 

 plain that the ground on which we are treading is 

 much more sure than that which served as our foot- 

 ing, while trying to discover facts in regard to the 

 primitive origin of life. While our knowledge as 

 to the origin of life is all hypothesis, and we are 

 not even sure of general facts, our knowledge of the 

 divergence of the great types from the Gastraea is 

 more than hypothesis, and of the general facts out- 

 lined in the last chapter we are tolerably sure. 

 Their truth is commensurate with that of the em- 

 bryological argument in general, and if we accept 



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