xr PHENOMENA OF ORGANIC NATURE 349 
inquire how far the remains contained in these 
fossiliferous limestones are able to convey any- 
thing like an accurate or complete account of the 
animals which were in existence at the time of its 
formation. Upon that point we can form a very 
clear judgment, and one in which there is no 
possible room for any mistake. There are of 
course a great number of animals—such as jelly- 
fishes, and other animals—without any hard parts, 
of which we cannot reasonably expect to find any 
traces whatever: there is nothing of them to pre- 
serve. Within a very short time, you will have 
noticed, after they are removed from the water, 
they dry up to a mere nothing ; certainly they 
are not of a nature to leave any very visible traces 
_ of their existence on such bodies as chalk or mud. 
Then again, look at land animals; it is, as I have 
said, a very uncommon thing to find a land animal 
entire after death. Insects and other carnivorous 
animals very speedily pull them to pieces, putre- 
faction takes place, and so, out of the hundreds of 
- thousands that are known to die every year, it is 
the rarest thing in the world to see one imbedded 
in such a way that its remains would be preserved 
for a lengthened period. Not only is this the 
~ case, but even when animal remains have been 
_ safely imbedded, certain natural agents may wholly 
destroy and remove them. 
Almost all the hard parts of animals—the 
bones and so on—are composed chiefly of phosphate 
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