44 



Objects for the Microscope. 



They are found in the living state abundantly in every 

 pond and ditch, ocean and rock-pool. They are in immense 

 deposits in every part of the world. A mud-bank, 400 

 miles long and 120 broad, has been found on the flanks of 

 Victoria Land, wholly composed of these siliceous valves, or 

 loricse. In Sweden and Norway they are used under the 

 name of bergh-mehl, and mixed with the flour for bread. In 

 the masses of guano these imperishable Diatoms are found in 

 profusion, having been eaten by shell-fish, re-swallowed by 

 the sea-bird, and passed through its digestive organs, to 

 reappear unharmed, in all their beauty, as you may see 

 them on the slides sold as " discs from guano." 



DIATOMS OF GUANO. 



It is not possible to catalogue the contents of the slides 

 sold as infusorial earths from various parts, because every 

 slide has a different collection, and the student should care- 

 fully study each slide, and learn its contents, with the help 

 of such a book as f Pritchard's Infusoria.' 



The earths from the following places contain some of the 

 most beautiful forms : 



Algiers 



Mull 



Bilin 



Italy 



Barbadoes 



Auvergne 



Richmond (discs) 



Bangor, U.S. 



New Durham 



Kieselguhr 



Lapland 



Gossa 



Obero 



Habitchtswald 



Tullamore 



Lock Mourn e 



Premnay 



Wreatham, U.S. 



NAVICDL^!. 



Virginia (discs) 



Piscataway 



Manchester, U.S. 



Rappanhanna 



Schockhoe 



Rugen 



Slieve Mor Hills 



Bermuda (discs) 



Some Diatomacese, however, are mounted separately, 

 either as test-objects, for their delicate striae, or for their 

 peculiar markings ; and none more frequently so than the 

 Naviculse, of which Navicula hippocampa, or Pleurosigma 

 angulatum, are favourite examples. 



