i8 95 . EOZOON AND THE MONTE SOMNA BLOCKS. 403 



Lavis been kind enough to show him such specimens in his collection 

 at Naples, he would probably have declined to acknowledge their true 

 affinity to Eozoon. But, of course, we must bear in mind the organic 

 possibilities in metamorphosed rocks which Brogger has so well 

 illustrated in Norway ; though even in Canada we cannot yet parallel 

 his Ovthis calligvamma moulded in garnet. 



The gradual discovery of new forms of pre-Cambrian life 

 in Europe and America, will soon compel palaeontologists to give 

 more attention to this neglected portion of their science. The dis- 

 coveries of Billings, Caye'ux, Walcott, Matthew, and others have 

 already established a probability that, besides Eozoon, the pre- 

 Cambrian rocks contain other stromatoporoid forms (Archaozoon 

 Cvyptozobn) as well as sponges, radiolarians, worms, and possibly 

 elementary types of mollusks and crustacea. Dr. Adams has also 

 made much progress in separating the truly sedimentary beds of the 

 Canadian Laurentian from those that may be referred to the crushing 

 and deformation of igneous products. Perhaps, however, the time 

 has scarcely yet come for summing up the evidence. 



J. William Dawson. 



Sir William Dawson's remarks call for some reply, as he seems 

 to have overlooked or misunderstood some points having an important 

 bearing. 



He distinctly passes over the table of necessary conditions for 

 the occurrence of eozoonal structure on pp. 264-65 of our paper, and 

 then describes the mode of occurrence of the so-called fossil in Canada, 

 which is provided for under section (b), on p. 265. All we require for 

 the formation of eozoonal structure is the contact of a rock containing 

 silicates, with a limestone more or less magnesian, both being exposed 

 to a high temperature. Whether such an association be due to the 

 injection of veins of igneous rock (either remaining as dykes or broken 

 up into separate masses) ; whether boulders of old volcanic or other 

 rocks containing silicates were enclosed at the time of the sedimenta- 

 tion of the limestone ; or whether beds of detrital silicates were inter- 

 stratified with limestones, does not matter. We repeat that all we 

 want is the association of these two types of rocks in close contact 

 with each other, and a sufficient supply of heat, time, and pressure. 

 Then, along the line of contact, both rocks will undergo alteration, 

 and this eozoonal structure be developed. 



Sir William Dawson expresses surprise at our statement that a 

 white pyroxene occurs as a leading constituent in the rock in which 

 the masses of Eozoon occur, and is at a loss to understand how it can 

 have been made. He assures us that it is entirely without foundation. 

 In reply, we refer Sir William Dawson to some of Dr. Carpenter's 

 choicest specimens, to some which he had photographed to illustrate the 

 "exhaustive memoir," which Sir William reminds us he intended to 



