ON A PIECE OF CHALK 71 



in the same way as that of the piece of chalk was made, 

 and view it with the microscope, it presents innumerable 

 GlobigerincB imbedded 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 Globigerince of the chalk, — 

 it is unnecessary to speak of them. 



GlobigerincB of every size, from the smallest to the largest, 

 are associated together in the Atlantic mud, and the cham- 

 bers 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 descrip- 

 tion. 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 ordi- 

 nary 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 sub- 

 stance 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 vast depths from which apparently living GlobigerincB 

 have been brought up, does not agree very well with our 

 usual conceptions respecting the conditions of animal life; 

 and it is not so absolutely impossible as it might at first 

 sight appear to be, that the GlobigerincB of the Atlantic sea- 

 bottom do not live and die where they are found. 



