Vol. 51.] FORMATION OF OOLITE. 207 



these latter really were tubules, it was remarkable that we observed 

 so few of them in transverse section, seeing that they must neces- 

 sarily have been cut at random in the preparation of the microscope- 

 slides. He did not at that juncture intend to discuss the origin of 

 oolite, as he felt that there was still much to be learnt concerning 

 the structure of oolitic grains both in the rocks and of recent 

 formation. The oolitic sand now forming in the Bahamas un- 

 doubtedly had tubules, as had been previously pointed out by 

 Prof. Judd. Many of the features presented by oolitic granule-, 

 and brought forward by the Author as evidence of the organic 

 origin of oolite, could be explained by the alteration effected in them 

 since their original formation. He did not say this in disparagement 

 of the Author's work, for he was much impressed with the profound 

 research displayed, the general excellence of it, and the conclusions 

 to which it had led him. A few days previously he (the speaker) 

 had demonstrated the existence of tubules in certain recent oolitic 

 granules from the United States. He would remind the Fellows 

 present that many years ago Dr. Carpenter described minute calculi 

 found in horses and other animals, which exhibited the most perfect 

 oolitic structure ; but ho (the speaker) did not wish at that moment 

 to discuss the origin of these. 



Mr. E. T. Newtoh" complimented the Author on his zealous 

 researches into the structure of oolitic rocks ; but while agreeing 

 with him that the irregular tubules termed Girvanella, and seen 

 sometimes within and sometimes on the outside of oolitic granules, 

 were of organic origin, he thought that the characteristic concentric 

 and radiated structure of oolitic granules was entirely different, and 

 not due to concentric tubules. The work of Rothpletz on the oolite- 

 sand of the Great Salt Lake made it highly probable that this 

 concentric structure also was due to some organism ; but this did 

 not seem to be satisfactorily established. 



Dr. G. J. Hlnde did not think that the Author was right in his 

 interpretation of the concentric layers so common in ordinary oolitic 

 grains as tubular forms of growth. In his (the speaker's) opinion 

 these concentric lines might indicate layers of growth, but they were 

 not in any sense tubules. Dr. Rothpletz had already, in his paper 

 ' On the Formation of Oolite,' in the Botanisches Centralblatt for 

 1892, declared his opinion that ' the majority of marine lime-oolites, 

 with regular zonal and radial structure, are of plant origin, produced 

 by the lime-secreting capacity of microscopically minute algae of low 

 position.' The very striking similarity in the microscopic structure 

 of the Great Salt Lake recent oolitic grains (as shown in sections 

 exhibited by the speaker) to that of Palaeozoic and later oolites 

 supported Dr. Pothpletz's opinion ; and if the algal origin of the 

 former should be confirmed, there could hardly remain any doubt 

 that the latter were similarly derived. 



Mr. A. C. Seward expressed himself in agreement with the main 

 contention in reference to the occurrence of organic tubular struc- 

 tures in the oolitic grains described by the Author of the paper. In 

 the case of some of the specimens he suggested that the tubules had 



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