606 WALTER H. BUCHER 
of odlites appears to have been generally misunderstood. ‘The 
cells of these primitive algae correspond in size to the largei forms of 
bacteria.‘ ' Bodies resulting from the precipitation of lime on or in 
the thick, jelly-like membrane surrounding the minute cells would 
therefore have a diameter fifty to a hundred times smaller than that 
of the odlites. Such bodies were, in fact, observed by Rothpletz in 
the odlites from Great Salt Lake as well as in those from the Red 
Sea, and were found to be mechanically incased in the odlites 
like the filamentous algae. “In quite delicate sections the calcare- 
ous substance [of the odlites}] . . . . is interrupted by scattered, 
minute granules. If we dissolve the section cautiously and slowly 
in very dilute acid, the granules remain behind exactly in their 
original position, and we recognize in them the dead and crumpled 
Gloeocapsa cells” (p. 280). 
From this it follows that if the Schizophyceae have at all an active 
part in the formation of odlites? it must be similar to that played by 
the closely related bacteria which separate calcium carbonate in 
the form of an emulsoid sol from solutions of calcium salts and 
thereby create conditions favorable for the growth of odlitic grains. 
The papers in which Wethered described Girvanella from many 
odlitic rocks of various ages‘ are, unfortunately, not accessible to 
me. The structure of certain calcareous odlites described by him, 
according to Rothpletz, seems ‘‘to have great resemblance to that 
of the Sinai odlite and is, perhaps, to be explained in the same 
manner.’ Others, however, judging from one of his figures repro- 
duced in Harker’s Petrology for Siudents,s represent true incrusta- 
‘Gloeocapsa: 2 in diameter; Gloeothece: 4-5 u long; Anthrax bacillus: 6 u 
long. 
2 Weighty reasons against this assumption were adduced by T. C. Brown, ‘Origin 
of Odlites and the Odlitic Texture in Rocks,” Bull. Geol. Soc. America, XXV (1914), 
754-57: 
3 As this process is probably due to a reaction of the calcium salts of the water with 
an alkaline excretion of the algae, we cannot, in this case, speak of “‘lime secreting”’ 
algae (cf. W. Pfeffer, The Physiology of Plants, I, translated by Ewart [Oxford, 1900], 
133). Compare Drew’s account of the action of denitrifying bacteria (Carnegie 
Institution of Washington, Publication No. 182, p. 30). 
4E. Wethered, ‘“‘On the Occurrence of the Genus Girvanella in Odlitic Rocks,” 
etc., Quar. Jour. Geol. Soc., XLVI (1890), 270-83; LI (1895), 196-206. 
5 Fourth ed., London, 1908, fig. 609, p. 261. 
ee 
