AMERICAN GEOLOGY THE EOZOON QUESTION. 645 



The fact that the lime-magnesian pyroxenes, through a process of 

 chemical metamorphism, passed over into serpentine, and that many 

 of the supposed sarcode chambers were tilled with granules of this 

 material in all stages of this alteration was from time to time noted 

 by Messrs. King and Kowne} T , Julien, Williams, Wadsworth, Merrill, 

 and others. The evidence thus presented was, however, wholly with- 

 out effect on Messrs. Carpenter and Dawson, who to the very last 

 remained true to their convictions, and as late as 1895 Dawson reviewed 

 the subject with seeming thoroughness and announced his original 

 opinion as unchanged. 



It remained, however, for J. W. Gregory and H. J. Johnston-La vis, 

 to give the deathblow to the theory as late as 1891 and 181)4. Gregory, 

 from an exhaustive study of Dawson's original specimen of the so-called 

 Tudor Eozoon, arrived at the conclusion that the same was wholly of 

 an inorganic nature. After a careful examination of all the slides and 

 figures, he wrote: 



I must confess myself absolutely unable to recognize in the specimen any trace of 

 the proper wall, canals, or stolon passages which are claimed to occur in Eozoon. 



The case against the organic nature of the specimen did not, how- 

 ever, rest upon negative evidence alone. The rock was intensely 

 cleaved and crumpled. The twin laminae in the planes of crystalline 

 cleavage in the calcite bands were, however, not bent. Further than 

 this, the bedding plane could be traced directly across the specimen, 

 traversing the limestone in the supposed body cavities. These facts 

 would seemingly prove conclusively that the supposed organic forms 

 were not original, but wholly secondary and due to metamorphism. 



Johnston-Lavis's later work was perhaps even more decisive, since 

 he showed that structures in every way similar could be produced by 

 the action of heat upon limestone. His conclusions were based upon 

 an examination of microscopic slides from blocks of limestone in the 

 volcanic tuffs of Monte Somma. To appreciate his evidence it must 

 be remembered that these blocks are ejected from the volcano and are 

 found embedded in a tuff consisting largely of pumiceous lava. They 

 occur as irregular, angular, or subangular masses ranging to more 

 than a cubic meter, though commonly less than a quarter of that size. 

 They have been acted upon by the heat and vapors of the volcano and 

 more or less completely metamorphosed, giving rise to various silicate 

 minerals, including pyroxene, olivine,, epidote, mica, etc. The struc- 

 ture of these altered limestones is entirely different from that of the 

 unaltered material, and corresponds in all details with those of the 

 original Canadian specimens, in many cases, on account of their fresh- 

 ness, exhibiting some of the pseudo-organic structure details — such as 

 stolon passages — in far greater perfection than does the true so-called 

 Eozoon. 



