I ON A PIECE OF CHALK 17 



to think at first, the mere powder and waste of 

 G-ldbigerince, 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 interesting dis- 

 covery that, not unfrequently, bodies similar to 

 these " coccoliths " were aggregated together into 

 spheroids, which he termed " coccospheres" So far 

 as we knew, these bodies, the nature of which 

 is extremely puzzling and problematical, were 

 peculiar to the Atlantic soundings. But, a few 

 years ago, Mr. Sorby, in making a careful examina- 

 tion of the chalk by means of thin sections and 

 otherwise, observed, as Ehrenberg had done before 

 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 to be identical ; and thus proved that the 

 chalk, like the surroundings, contains these mys- 

 terious coccoliths and coccospheres. Here was a 

 further and most interesting confirmation, from 

 internal evidence, of the essential identity of the 

 chalk with modern deep-sea mud. Globigerince, 

 coccoliths, and coccospheres are found as the chief 

 constituents of both, and testify to the general 

 similarity of the conditions under which both have 

 been formed. 1 



The evidence furnished by the hewing, facing, 



1 I have recently traced out the development of the "cocco- 

 liths " from a diameter of y^^th of an inch up to their largest 



VOL. VIII C 



