M. Otto Hahn on Eozoon canadense. 281 



indeed, the canal-sjstems in gneiss must of themselves alone 

 be explained as of organic origin. I admit that I Avas for a 

 moment doubtful whether analogy for these structures in gneiss 

 might not be found in the sponges. I had, however, to re- 

 nounce this charming idea when I found that the canal- 

 systems consisted of quartz which traversed the felspar. Here 

 I would recommend the further examination of this hitherto 

 unobserved phenomenon ; I believe that it throws a new light 

 upon the formation of gneiss. 



It certainly does not conduce to exactness of inference if, 

 for the organic creature that is supposed to have been dis- 

 covered, we can find no complete analogue, and, for its separate 

 parts, again at least no exactly similar part in another creature. 

 Polytrema is regular. With the Acervulince, Avith which Max 

 Schultze arranges Eozoon, it has nothing in common except 

 irregularity — in such matters a resemblance of very doubtful 

 value. The Calcannce have quite regularly arranged canal- 

 systems. The circumstance that our zoologists are accus* 

 tomed to preparations very difierent from rocks, and that they 

 have a preconceived notion that any symmetrical structure 

 cannot be inorganic, contributed not a little to the confusion. 

 I need only refer to the microscopic picture of the pitchstone 

 of Arran. But no rock is more deceptive in this respect than 

 serpentine. This greenish yellow transparent mass, with its 

 peculiar trembling lustre (caused by hyaline crystals) looks so 

 deceptively like sarcode, that it must not be taken amiss of a 

 zoologist if he is unable to tear himself free from the ideas 

 that press upon him at the first glance. If now, unfortunately, 

 the worm-like form is superadded, if the sarcode mass is 

 further clothed with an asbestos layer, and, lastly, we see 

 further " dentine-" and canal- or branch-systems, then it is 

 too much. Can it surprise us if another finds verrucose pro- 

 cesses? And yet nothing but illusion. Only a small amount 

 of quiet observation would at once have led back to the truth. 

 The observer must in fact have been puzzled at once by the 

 single fact that the canal-systems do not consist of serpentine 

 mass ; and this a glance into the microscope with polarized 

 light would immediately have shown. The canal-systems 

 always penetrate the chamber-walls of the Operculince. Here 

 there is no trace of this, but rather a completely different filling 

 mass in the two. Nay a single olivine grain or calcareous 

 fragment in a chamber of Eozoon must fairly raise the question, 

 How can an olivine grain get into the chamber of a Fora- 

 minifer? On more careful observation, moreover, chambers 

 existing quite alone (?*. e. grains) would have been found. 

 The chrysotile shell also is not regularly present ; Avhere 



Ann. & Mag. N. Hist. Ser. 4. Vol. xvii. 19 



