170 Reviews — Dawson^ s Dawn of Life. 



as completing the conditions of these Foraminiferal reefs of the period, 

 and Dr. Dawson alludes to the outspread fragments of Eozomi in the 

 rock far away from the reef. 



Dr. Dawson in his " Dawn of Life " gives the details of the history 

 of this discovery, together with an account of the Laurentian rocks ; 

 and, reprinting the papers and memoirs by Logan, Hunt, and others, 

 treating of these matters, he points out the new localities for Eozoon, 

 and additional facts illustrating its structure, especially due to careful 

 and reiterated examinations by Dr. Carpenter. Dr. Dawson recog- 

 nizes E. Canadense, with its varieties minor and acervidina, besides 

 E. Bavaricum, of Giimbel. Objections (treated of in Chapter VIL) 

 have been raised to the notion of the said laminated serpentine-lime- 

 stone of Canada containing traces of organic structure ; and the 

 granules, threads, brushes, and filaments of magnesian silicates, 

 which are construed by Dawson and Carpenter as infillings of fora- 

 miniferal chambers, passages, canals, and tubules, traversing a 

 calcareous test, have been regarded as deposits, metamorphs, or 

 pseudomorphs of the silicates and limestone, like some apparently 

 analogous mineral formations, such as various segregations and con- 

 cretions, dendritic, coralloid, laminated, filamentous, etc.^ Both of 

 these kinds of mineral arrangement, one due primarily to organic, 

 and the other to purely inorganic processes, probably exist in such 

 serpentinous limestones as those referred to, just as both mineral 

 dendrites and real Conferval organisms exist in Lidian chalcedonies ; 

 and as both creeping oxides and real Sponge-tissue are severally re- 

 cognizable in flint. For the particular Canadian limestone under 

 notice, the acceptation of a foraminiferal shell, quite within the 

 zoological limits of known Ehizopodal life, and affected by mineral 

 infiltration, similar to the glauconitic infillings of the shells and 

 skeletons of various recent and fossil organisms, seems to be a natural 

 ex23lanation for the phenomena to be accounted for. 



It has been remarked that Eozoon occurs only in metamorphosed 

 rocks, whether in America or Europe, and therefore must be a pro- 

 duct of metamorphism ; but it is replied that it is a fossil peculiar 

 to such very old rocks as have happened to be subject to metamor- 

 phic agencies from their position. We may add that perhaps some 

 of the green grains in the soft unaltered old Silurian clays of Kussia 

 may be Eozoonal ; and some of those figured by Ehrenberg have 

 such an appearance. 



Principal Dawson has brought together his own and Dr. Carpenter's 

 observations on the structure of Eozoon, whether silicated or not, — for 

 in some instances the calcitic layers remained channelled and per- 

 forated without any infillings, though difficult to be rightly seen 

 except by an exjDert, and only with a high-class microscope. That 



^ Some very curious minute imitative forms presented by coke are figured and 

 described in the Phil. Mag. for January, 1876, by Mr. E. T. Newton, F.G.S. We 

 might be disposed at first sight to set them in rivalry to some of the Eozoic structures ; 

 but the encrinitoid, zoophytoid, plumoid, and other forms of the coke do not reach 

 such an exact state of similitude, much less do they all so definitely represent parts of 

 one structure, as to support the idea of their being analogues of the particular serpen- 

 tinous Eozoonal bodies above referred to. 



