106 THE CANADIAN NATURALIST. [April 



the specimens from Grenville and the Calumet show the structures 

 of the laminae with nearly equal distinctness whether the chambers 

 have been filled with serpentine or pyroxene, and that even the 

 minute tubuli are penetrated and filled with these minerals. On 

 the other hand, there are large specimens in the collection of the 

 Canadian Survey, in which the lower and older parts of the masses 

 of Eozobn are mineralized with pyroxene, and have to a great 

 extent lost the perfection of structure which characterizes the more 

 superficial parts of the same masses, in which the chambers have 

 been filled with a light green serpentine. Dr. Sterry Hunt has 

 directed his attention to the conditions of deposit of these minerals, 

 and will, I have no doubt, be able satisfactorily to explain the 

 manner in which they may have been introduced into the chambers 

 of the fossils without destroying the texture of the latter. 



It is due to Dr. Sterry Hunt to state that, as far back as 1858, 

 in a paper published in the Quarterly Journal of the Geological 

 Society,* he insisted on certain chemical characters of the Lauren- 

 tian beds as affording " evidence of the existence of organic life 

 at the time of the deposition of these old crystalline rocks"; and 

 that he has zealously aided in the present researches. 



I may also state that Mr. Billings, the palaeontologist of the 

 Survey, has joined in the request that I should undertake the 

 examination and description of the specimens, as being more 

 specially a subject of microscopical investigation. 



Before concluding this part of the subject, it is proper to 

 observe that the structures above described can be made out only 

 by the careful study of numerous slices, and in some instances 

 only with polarized light. Even in the more perfect specimens of 

 Eozoon, as those accustomed to such researches will readily under- 

 stand, *the accidents of good preservation and the cutting of the 

 slices in the proper place and direction must conspire in order to 

 a clear definition of the more minute structures. 



It is also to be observed that the specimens present numerous 

 remarkable microscopic appearances, depending on crystallization 

 and concretionary action, which must not be confounded with 

 organic structure. It would be out of place to give any detailed 

 description of them here ; but it is necessary to caution observers 

 unaccustomed to the examination of mineral substances under the 

 microscope, as to their occurrence. I may also mention that the 



* Vol. xv, p. 493. 



