I ON A PIECE OF CHALK 13 



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, 

 grayish 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 

 G-lobigerinw embedded in a granular matrix. Thus 

 this deep-sea mud is substantially chalk. I say 

 substantially, 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 Gflobigerince of the chalk, it is un- 

 necessary to speak of them. 



Globigerince 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 Globigerina 

 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 observa- 

 tion 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, 



