M. Otto Halm on Eozoon canadense. 275 



supposed organism can be recognized as mere rock-structure. 

 It is only if all the essential characters of the Foraminifer, 

 and indeed each for itself, are no mere rock-structures, that 

 the proof from analogy is carried at least to a high degree of 

 probability. But if tlie inorganic nature of only one is proved, 

 the chain of evidence is broken. 



From all this the course of investigation becomes a matter 

 of necessity. All existing serpentine limestones (ophicalcites) , 

 all serpentines and primary limestones by themselves, and, 

 further, also the minerals occurring under certain circumstances 

 in the serpentine limestone, must be investigated with respect 

 to their nature and their relations to the serpentine limestone. 

 But when this is done, a large field opens to the geologist. 

 Now the question is, do the ^02;oon-structures occur in any 

 other rock or not, whether with all the characters together or at 

 least some of them ? Upon this it becomes his duty to examine' 

 microscopically as to this point all primary and metamorphic 

 rocks, nay, even the rocks of the whole sedimentary series. I 

 have followed the course indicated, and then, and not before', 

 allowed myself to form a judgment upon the zoological facts 

 which had been advanced. In what follows I shall undertake, 

 first, the criticism of the geological, then of the mineralogical, 

 and, lastly, of the zoological facts. 



1. The Oeological Facts. 



The Eozoon-s,ix\xci\xxQs occur in lenticular or spheroidal 

 nodules of serpentine limestone in the limestone of the Lauren- 

 tian formation of Canada. The limestones belong to gneiss 

 strata, the earliest sedimentary rocks. They are mere enclo- 

 sures. Are they merely imbedded in the limestone, and there- 

 fore formed before it, or were they produced simultaneously 

 with it ? This question can be decided only on the spot. It 

 is most probable that they were imbedded as ready-formed 

 nodules ; but this is not necessary. If the serpentine-mass 

 was, as it must have been at the time of the formation of the 

 Eozoon, still in a fluid state, it must also have found other 

 cavities in the limestone, and have filled these. But we have 

 no account of any such cavities. Hence the first supposition 

 is the more probable. 



Eozoon is said to occur not only in Canada, but also in the 

 most various parts of the earth. Glimbel has found it in the 

 Bayerische Wakl, Hochstetter in Bohemia (Krummau), and 

 Pusgrewski in Finland. I have examined some of the hand- 

 specimens of the two first named and found in them no Eozoon- 

 structures, or at least not all the described characters together. 



