XI 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 



