ix.] ON A PIECE OF CHALK. 159 



commences, and gradually leads, for about 300 miles, to the 

 Newfoundland shore. 



Almost the whole of the bottom of this central plain (which 

 extends for many hundred miles in a north and south direction) 

 is covered by a fine mud, which, when brought to the surface, 

 dries into a greyish-white friable substance. You can write with 

 this on a blackboard, if you are so inclined ; and, to the eye, it is 

 quite like very soft, greyish chalk. Examined chemically, it 

 proves to be composed almost wholly of carbonate of lime ; and 

 if you make a section of it, in the same way as that of the 

 piece of chalk was made, and view it with the microscope, 

 it presents innumerable Globigerincc embedded in a granular 

 matrix. 



Thus this deep-sea mud is substantially chalk. I say substan 

 tially, because there are a good many minor differences ; but as 

 these have no bearing on the question immediately before us, 

 which is the nature of the Globigerincc of the chalk, it is 

 unnecessary to speak of them. 



GlobigerincR of every size, from the smallest to the largest, are 

 associated together in the Atlantic mud, and the chambers of 

 many are filled by a soft animal matter. This soft substance is, 

 in fact, the remains of the creature to which the Q-lobigcrina 

 shell, or rather skeleton, owes its existence and which is an 

 animal of the simplest imaginable description. It is, in fact, a 

 mere particle of living jelly, without defined parts of any kind 

 without a mouth, nerves, muscles, or distinct organs, and only 

 manifesting its vitality to ordinary observation by thrusting out 

 and retracting from all parts of its surface, long filamentous 

 processes, which serve for arms and legs. Yet this amorphous 

 particle, devoid of everything which, in the higher animals, we 

 call organs, is capable of feeding, growing, and multiplying ; of 

 separating from the ocean the small proportion of carbonate of 

 lime which is dissolved in sea-water ; and of building up that 

 substance into a skeleton for itself, according to a pattern which 

 can be imitated by no other known agency. 



The notion that animals can live and flourish in the sea, at the 



