Appendix D: Preparation of Microscopical Material 217 



To see the macronucleus and the micronucleus use a drop of a 

 2 per cent, solution of acetic acid or, better, methyl green (Appen- 

 dix B, reagent 56) . 



e) Permanent mounted preparations. Benedict's method is 

 as follows: 



"Smear a glass slide with albumen fixative, as in preparing for 

 the mounting of paraffin sections. Then place on the surface of 

 the film of fixative a drop or two of water containing the forms 

 which it is desired to stain. Let nearly all the water evaporate 

 by exposure to the air of the room until only the film of fixative 

 remains moist. The slide can now be immersed in Gilson or any 

 other fixing reagent, and then passed through the alcohols, stains, 

 etc., in the same way that mounted sections are handled. 



" I have had no difficulty in getting preparations of Paramoe- 

 cium by this method, with very little distortion of the body, and 

 any kind of staining desired. By this method students can pre- 

 pare in ten minutes very satisfactory preparations of protozoa for 

 demonstration of nuclei, etc." Journal of Applied Microscopy, 

 Vol. VI, p. 2647. 



SPONGES 



To isolate the spicules of calcareous sponges boil a bit of the 

 sponge in 5 per cent, solution of caustic potash for a few minutes. 



Fairly thick transverse, longitudinal, and tangential sections 

 of Grantia showing spicules in the tissues are useful. Make 

 these with an old razor or sharp scalpel. To hold the object 

 while sectioning, place it between two pieces of pith or cork. For 

 a careful study of the relations of the two systems of canals in the 

 body-wall, thinner sections are necessary. To prepare these it is 

 best to decalcify (2 per cent, chromic acid, 24 to 36 hours) the 

 sponge and cut celloidin or paraffin sections on the microtome 

 although fairly good sections may be made by hand. They 

 should be dehydrated and mounted in balsam if permanent prep- 

 arations are desired; if not, they may be examined in glycerin. 



To color the collar cells use an aqueous solution of aniliii blue. 



Spicules of silicious sponges are isolated by treating bits of 



