Vol. 51.] FORMATION OF OOLITE. 209 



appreciable difference from that of ordinary calcareous concretions 

 of a purely inorganic origin : similar radiating and concentric struc- 

 tures being also met with in the spherulites frequently present in 

 eruptive rocks. Difference in the orientation of crystalline grains 

 or fibres might account for some of the appearances which the outer 

 layers of the oolitic bodies exhibited. The later layers, deposited 

 around a nucleus of irregular form, did not necessarily follow the 

 contours of the nucleus. 



Prof. A. H. Green also spoke. 



The Author thanked the President and Fellows for the way in 

 which his paper had been received. Opinions had evidently under- 

 gone some modification since he first appeared before the Fellows, 

 and advocated the organic origin of oolitic granules. The truth of 

 this principle seemed to be now admitted ; but there was difference of 

 opinion on matters of detail. He quite agreed that there was 

 much yet to be done in this direction. He was afraid that he had 

 not made it clear that the concentrically growing tubular forms of 

 growth were not identical with Girvanella, though they might be 

 allied to this genus. There were many forms of growth which 

 might be called oolite-producing organisms. 



In reply to Dr. Hinde, the Author stated that the sliced ends 

 of tubular forms of growth could be detected, though often with 

 difficulty. This was not to be wondered at considering the frail 

 nature of the organisms, the pressed condition in which they appear 

 in the granules, and the mineralogical changes to which they have 

 been subjected. 



