Principal J. W. Dawson onJLozoon canadense. 37 



loped in serpentine. (5) Crystalline cavities, fluid-cavities, 

 &c., in minerals, which, when carefully studied, show a definite 

 relation to the crystallization, quite different from- the canals 

 o^Eozoon. (6) Fibrous vegetable and animal substances, as 

 the fibres of Vaucheria sometimes beautifully preserved in 

 moss-agates, the fibrous structure of sponges and of certain 

 zoophytes. (7) Porous shells and crusts. More especially I 

 have found the shells of Se^-jjulce, of certain Brachiopods, of 

 Hyolithes, of Trilobites, and of certain parts of crinoids to 

 present, when injected with mineral substances, appearances 

 very similar to that of Eozoon and other Foraminifera. All 

 of these and other mineral and organic structures have actually, 

 in the progress of the researches on Eozoon^ been under exam- 

 ination ; and my own collection contains slices and other pre- 

 parations of them, accumulated for this special purpose. No 

 doubt, after all this care, mistakes may be made ; but I think 

 it right to mention the precautions which have actually been 

 taken, before launching the doctrine of Laurentian life on an 

 incredulous world. 



In conclusion, while I must regard Hahn as deserving of 

 some blame for his want of attention to the labours of others, 

 and for the partial and limited way in which he regards the 

 subject, he deserves credit for the minuteness with which he 

 has examined the particular specimens which he has studied ; 

 and I trust that when his information as to facts shall have 

 become more complete, his theoretical views will be very much 

 modified. 



Postscript. 



Since mailing the above communication, I have received the 

 May number of the 'Annals,' containing the second Review 

 with which its correspondents have honoured my little book 

 ' The Dawn of Life.' This review does not, however, induce 

 me to modify any thing I have stated above, nor does it re- 

 quire any detailed reply in the interest of scientific truth, 

 since, though sufiiciently rich in personal references, it contains 

 no newfacts of any importance to the discussion, and the want of 

 fairness in its treatment of the book will be sufficiently ai)])arent 

 to any one who has the work to refer to. Should my book have 

 the good fortune to go into a second edition, I shall endeavour to 

 give the review such attention as it deserves. In the mean time 

 I am devoting the few hours I can spare for such work to a 

 reexamination of the Palasozoic serpentines and ophiolites of 

 this country, with the view of illustrating the precise condi- 

 tions under which corals and other familiar fossils occur in 

 these rocks ; and the facts thus obtained may perhaps furnish 



