208 ME. E. B. WETHERED ON THE [MayiSo^, 



not served as centres for the deposition of carbonate of lime, bat bad 

 more probably bored their way into the substance of the calcareous 

 nucleus. The explanation offered by the Author with regard to the 

 radiating structure seen in certain grains he regarded as unsatis- 

 factory, their general appearance being much more suggestive of 

 secondary changes in the oolitic grains, which had no direct 

 connexion with the Girvanella-tuhules. 



Prof. Judd said that so far back as 1862 the eminent botanist 

 Dr. Ferdinand Cohn had pointed out the important part played by 

 algae in the formation of the Sprudelstein of Carlsbad and other 

 calcareous rocks. At a later date Bornet, the eminent French 

 algologist, had insisted no less strongly on the work done in perfor- 

 ation and breaking-up of calcareous fragments by other plants. The 

 speaker, while insisting on the value and importance of the results 

 obtained by Mr. Wethered and other workers in this field of research, 

 was inclined to regard some of the structures (especially certain of 

 the radial ones) as due to the action of destructive rather than to 

 constructive organisms. 



Mr. H. B. Woodwaed referred to the modern formation of oolite- 

 grains in waters charged with bicarbonate of lime, whether in 

 proximity to calcareous springs or coral-reefs. In the Jurassic 

 rocks we find the frequent association of oolite with coral-bed^. 

 In the Lower Lias limestone oolitic structure is uncommon, but 

 good examples occur at Applecross in Ross-shire ; and it is interest- 

 ing to note that there the oolitic beds occur in conjunction with 

 bands of coral-rock, while not far away is the remarkably fine coral- 

 bed of Lussay, near Broadford, in Skye. He thought that the 

 slides exhibited by the Author did not show connexion between 

 the Girvanella and the concentric and radiate bands of oolite- 

 grains. The carbonic acid abstracted from water during algous 

 growth might, however, lead to the precipitation of carbonate of 

 lime. 



Prof. Seeley believed that some of the photographs shown by 

 Mr. Wethered exhibited a structure which, although imperfectly 

 preserved, might be compared with the sections of nullipores which 

 the speaker brought before the British Association at Bath in 1888, 

 as evidence that some grains of oolite are of organic origin. He 

 had been led to that conclusion originally by finding in the Portland 

 oolite polygonal grains such as occur where nullipores branch, and 

 microscopic examination had supported the inference. In the 

 discussion at Bath, Mr. G. K. Gilbert first described the circumstances 

 under which oolitic grains are found on the shores of the Great 

 Salt Lake. And it was interesting that the microscopic structure of 

 those grains, which was subsequently made known, had given similar 

 evidence of organic origin. 



Mr. Rutley said that, with regard to the nuclear portions of some 

 of the sections projected upon the screen, he considered that the 

 Author was probably correct in ascribing an organic origin to the 

 interlacing tubular structures ; but, so far as the peripheral portion 

 of the oolitic bodies was concerned, he believed that it presented no 



