274 M. Otto Hahn on Eozoon canadense. 



wart-like superficial processes. Max Schultze states that after 

 the calcination of the rock the canal-systems were coloured 

 black ; and from this he concludes that their contents were of 

 organic nature. 



I could only repeat what is well-known, if I were to repro- 

 duce here the present position of the controversy. Zirkel has 

 given a thorough representation of the contradictory opinions 

 (' Die raikroskopische Beschatfenheit der Mineralien und 

 Gesteine/ Leipzig, 1873, p. 313). As regards Max Schultze, 

 I may refer the reader to the * Verhandlungen des naturhisto- 

 rischen Vereins der Preussischen Rheinlande und Westphalens,' 

 Jahrg. XXX. p. 164, unfortunately an incomplete work of the 

 celebrated naturalist. 



There are consequently two opinions. One maintains the 

 organic nature of Eozoon ; the other disputes it. The former 

 supports itself upon analogous facts in the animal kingdom, 

 both extinct and living. The latter holds that it can also cite 

 analogies in favour of the assumption of peculiar rock-forma- 

 tions. Few leave the question open. 



I thought it best to adopt the following mode of investi- 

 gation. 



I started from the proposition that for every part of a rock 

 the presumption is in favour of mere rock- formation. If the 

 organic nature of a portion of the rock is affirmed, the onus 

 prohandi lies upon those who make the assertion, and, until 

 full proof to the contrary, the presumption remains in force. 



But in the present case we stand immediately in face of a great 

 difficulty. What are the characters of an organic being ? The 

 same structure, and especially the same structures together (as 

 is admitted by Carpenter and his allies), occur neither in extinct 

 nor in living organic creatures ; but it is rather stated that the 

 individual parts of the ^o^oo/t-structure are only to be recog- 

 nized in different kinds of Foraminifera. 



This circumstance alone makes the proof very doubtful. 

 But to this must be added the fm-ther fact that the zoologists, 

 and especially the best of them, are least inclined, and indeed 

 least in a position, to know and test all existing rock-structures. 

 The position of the geologist is therefore all the more un- 

 favourable. His proofs are scarcely considered ; and even other- 

 wise it is difficult to get their value as proof duly estimated ; 

 Avhilst the zoologist is in the happy position of being able to 

 throw into the scale the Brennus's sword of authority, espe- 

 cially when the microscope is in question. 



The position of the two can only be equalized if it be ad- 

 mitted that mere analogy is incapable of furnishing the proof 

 of the organic origin of Eozoon ; and that, further, no part of the 



