THE DAWN OF LIFE 169 



seas. Loganite, the mineralizing substance of the 

 Burgess Eozoon, is different from serpentine, yet 

 closely allied to the glauconites. The presence 

 of pyroxene may be explained in a similar way. 

 It is a frequent constituent of bedded volcanic 

 rocks and of volcanic ashes, and beds of it occur 

 in the Grenville series which once, no doubt, were 

 ash-beds. Layers of it also occasionally occur 

 from a similar cause in the limestone, and crystals 

 of it have been deposited by water in the veins 

 passing through the limestones and schists. Dr. 

 Johnston-Lavis has described in the July number 

 of the Geological Magazine for 1895 the aqueous 

 deposition at ordinary temperature of crystals of 

 pyroxene and hornblende, in cavities and crevices 

 of bones included in an ash-bed of recent date, 

 and in presence of calcite, apatite, and fluoride of 

 calcium, as in the Grenville series. This is a 

 modern instance analogous to that suggested above. 

 Hence all these minerals filling the cavities and 

 canals of Eozoon may have been deposited by 

 water at ordinary temperatures, and have no con- 

 nection with the alteration to which the beds have 

 been subsequently subjected. 



I may add here that a Tertiary glauconite from 



