120 THE MICROSCOPE. Auff 



o- 



iu fluid, either weak sj^irit or Goody's solution answered 

 very well. But many of the palates, especially those of 

 the marine gastropods, become most beautiful objects for 

 the polariscope when they are mounted in Canada bal- 

 sam, the form and arrangement of the teeth being very 

 strongly brought out by it and a gorgeous play of colors 

 being exhibited when a selenite is phiced behind the ob- 

 ject, and the analysing prism is made to rotate." 



This is all very well for the novice in microscopy but 

 I think I can show a better way for preparing odonto- 

 phores. Let us suppose we have a Helix, like that men- 

 tioned as caught above, or a Limuae or Physa or Planorbis 

 which are so common everywhere. We have but to put 

 the shell containing the animal alive into boiling strong 

 caustic potash and bring it to a boil. The strength of 

 the potash solution must be suited to the animal, some 

 being destroyed, and the odontophore also, by strong 

 solution, then wash it in water. All will be dissolved 

 but the shell and the odontophores. This can have the 

 shell taken out and the odontophore searched for by 

 holding the vessel in which the boiling has gone on, up to 

 the light. The odontophore will be seen to be floating 

 about and flashing by reflected light. It can be taken 

 out with with a pipette and thorouglily washed. It is 

 then put on a slide and arranged by means of two needles 

 put into handles. I find the needles can be thrust in- 

 to matches, the end with the eye in it first, and the front 

 end used. When the odontophore has been arranged 

 any preservative having glycerine in it cannot be used, for 

 glycerine is liable to dissolve any time in the substance 

 as Carpenter showed. So the odontophore must be 

 dried on the slide and the cover put on afterwards. A 

 ring of gold size being put around the preparation and 

 dried before the cover is put on, or gum thus is used to 

 mount it, and I find gum thus is excellent, much better 

 than balsam and showing the colors with polarized light 



