56 ON A PIECE OF CHALK 



live the supposition that these organisms have been 

 swept by currents from the shallows into the deeps of 

 the Atlantic. 



It therefore seems to be hardly doubtful that these 

 wonderful creatures live and die at the depths in which 

 they are found. 



However, the important points for us are, that the 

 living Globigerince are exclusively marine animals, the 

 skeletons of which abound at the bottom of deep seas ; 

 and that there is not a shadow of reason for believing 

 that the habits of the Globigerince of the chalk differed 

 from those of the existing species. But if this be true, 

 there is no escaping the conclusion that the chalk 

 itself is the dried mud of an ancient deep sea. 



In working over the soundings collected by Captain 

 Dayman, I was surprised to find that many of what 

 I have called the "granules" of that mud, were not, 

 as one might have been tempted to think at first, the 

 mere powder and waste of Globigerince, but that they 

 had a definite form and size. I termed these bodies 

 " coccoliths," and doubted their organic nature. Dr. 

 Wallich verified my observation, and added the inter- 

 esting discovery, that, not unfrequently, bodies simi- 

 lar* to these " coccoliths " were aggregated together into 

 spheroids, which he termed " coccosptwres." So far as 

 we knew, these bodies, the nature of which is ex- 

 tremely puzzling and problematical, were peculiar to 

 the Atlantic soundings. 



But, a few years ago, Mr. Sorby, in making a care- 

 ful examination of the chalk by means of thin sections 

 and otherwise, observed, as Ehrenberg had done be- 

 fore him, that much of its granular basis possesses a 

 definite form. Comparing these formed particles 

 with those in the Atlantic soundings, he found the two 



