308 THE FOEAMINIFEEA 



workers use black ribbed silk to cover the sorting 

 tray, fastened so that the ridges of the silk run 

 horizontally, or from left to right ; this will pre- 

 vent the specimens from rolling when the microscope 

 is inclined for comfort in observation. A useful 

 form of tray for sorting purposes may be made 

 of black vulcanite (ebonite), and rimmed round as 

 before ; this material, however, loses its black surface 

 after a year or two, but can then be reblackened 

 with a smooth quick-drying varnish. 



Some preliminary sorting may be carried out in a 

 mechanical way by taking advantage of the forms of 

 the shells. For example, in a medium sifting from an 

 ooze, by tilting the tray the Orhidince will first roll 

 dowm, and on further inclining it the Globigeriucp 

 and PullenicE. Discoidal forms will remain behind 

 after all the other particles have been made to roll 

 off by a gentle persuasive tapping. 



0)1 Mounting the Shells of Foraminifera. — For 

 the ordinary purposes of mounting, the opaque 

 wooden cell introduced by Dr. Carpenter may be 

 adopted (fig. 40). It is a strip of wood 3 inches by 

 1 inch, wath a hole bored in the centre. To this 

 wooden slip a thin piece of cardboard is glued, 

 which has been previously blackened in the middle 

 with Indian ink, to form a background. Several 

 slips may be mounted at one time on a long strip 

 of cardboard measuring a little more than 3 inches 

 in width, and having a broad black stripe along 

 the centre, and put under pressure; when dry the 

 slips can be cut round with a sharp penknife. 



