668 



3. Exoskeleton formed of real bone ; partly in association 

 with homogeneous osteoid substance (ganoin) and 

 dentinal tubes. 



Scales of Ganoidei, of Lepidosiren, some Siluroidei, of Mor- 

 myri, many Characini and Clupeini, also of Thynnus. 



In terminating this communication, I think it proper to mention 

 that the great liberality with which my friend Mr. Tomes of London, 

 and Professor Williamson of Manchester, put their large collections of 

 microscopic preparations of teeth, bones, and scales at my disposal, 

 proved of great assistance in my investigations, and, accordingly, I 

 am only fulfilling an agreeable duty in now publicly expressing my 

 obligations to them. I am also greatly indebted to my friends Filippo 

 de Filippi of Turin and Henry Miiller of Wiirzburg, also to Dr. 

 Hyrtl of Vienna, and Dr. Peters of Berlin, who supplied me with 

 many of the rarer Mediterranean and foreign fishes. But, in order 

 that my observations may yield the results which may not unrea- 

 sonably be expected from them, I need more aid ; and as England 

 is the country in which not only the largest zoological collections of 

 fishes, but also the greatest number of microscopic preparations of 

 the hard tissues of recent and fossil animals, are to be found, I take 

 the liberty to ask the possessors of such collections who may be 

 interested in this matter to favour me with such specimens as may 

 seem to them calculated to give to this series of observations the 

 greatest possible extension. 



III. " On the Physical Phenomena of Glaciers." Part II. By 

 Dr. TYNDALL, F.R.S. Received February 24, 1859. 



[Abstract.] 



The main portion of this Paper deals with the veined structure of 

 glacier ice. The author refers to his observations in the Mer-de-glace 

 in 1 857, and his reasons for withholding them, and visiting the glaciers 

 once more in 1858. 



He describes the general aspect of the structure, and examines the 

 two theories of the phenomenon which are now deserving of attention ; 

 one of these considers the blue veins to be a continuation of the bed- 



