I ON A PIECE OF CHALK 17 



to think at first, the mere powder and waste of 

 Globiycrinoc, but that they had a definite form and 

 size. I termed these bodies &quot; coccoliths&quot; and 

 doubted their organic nature. Dr. Wallich verified 

 my observation, and added the interesting dis 

 covery that, not unfrequently, bodies similar to 

 these e: coccoliths &quot; were aggregated together into 

 spheroids, which he termed &quot; coccospheres&quot; 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. Gloligcrinw, 

 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 &quot;cocco 

 liths &quot; from a diameter of T15 Vj7th of an inch up to their largest 



VOL. VIII C 



