100 THE DAWN OF LIFE. 



feral shells^ the answer is that they are both products 

 of one kind of locality. The same sea bottoms in 

 which Foraminifera most abound are also those in 

 which for some unknown chemical reason glauconite 

 is deposited. Hence no doubt the association of this 

 mineral with the great Foraminif eral formation of the 

 chalk. It is indeed by no means unlikely that the 

 selection by these creatures of the pure carbonate of 

 lime from the sea- water or its minute plants, may be 

 the means of setting free the silica, iron, and potash, 

 in a state suitable for their combination. Similar 

 silicates are found associated with marine limestones, 

 as far back as the Silurian age ; and Dr. Sterry Hunt, 

 than whom no one can be a better authority on chemi- 

 cal geology, has argued on chemical grounds that 

 the occurrence of serpentine with the remains of 

 Eozoon is an association of the same character. 



However this may be, the infiltration of the pores 

 of Eozoon with serpentine and other silicates has 

 evidently been one main means of the preservation of 

 its structure. When so infiltrated no metamorphism 

 short of the complete fusion of the containing rock 

 could obliterate the minutest points of structure ; and 

 that such fusion has not occurred, the preservation in 

 the Laurentian rocks of the most delicate lamination 

 of the beds shows conclusively; while, as already 

 stated, it can be shown that the alteration which has 

 occurred might have taken place at a temperature far 

 short of that necessary to fuse limestone. Thus 

 has it happened that these most ancient fossils have 



