88 THE MICROSCOPE. June 



So much for the Protococcus ; and now how to pre- 

 serve them for future reference. When examined chemi- 

 cally they are found to be made up of protoplasm colored 

 with green coloring matter. No siliceous or woody tis- 

 sue is present so that the microscopist is puzzled to fix 

 them and to have a medium which will preserve them 

 intact. For years I have tried various ways of mount- 

 ing them and even neglected the mounting in carbolic 

 acid for that was unreliable. I think now that I have 

 got a way for mounting Protococcus and even animal- 

 cules which are transparent and formed of protoplasm 

 alone. These latter, it is known, must hitherto be 

 studied alive for they cannot be preserved, or at least 

 could not until I tried the process I am about to de- 

 scribe. But I do not claim the process as applicable to 

 animals. I only say that I think they will do with it. 



To describe : I take the Protococcus and kill it by a 

 saturated solution of Salicylic acid. This will kill any- 

 thing be it vegetable or animal or Protista. Then wash- 

 ing the acid with water, I introduce a weak solution of 

 ammonia (household ammonia) ; to this is added a few 

 drops of a solution of Grum Thus in alcohol, or wood 

 spirit and it is permitted to stand for a day in an un- 

 covered vessel. The ammonia will go off, and likewise 

 the alcohol, in a great degree. We have then a solution 

 of Gum Thus in water. This is evaporated down at the 

 ordinary temperature of the house, 60° F. until we have 

 the Protococcus in a strong solution of Gfum Thus. 

 More Gum Thus is added and mounted in the usual man- 

 ner in which Canada Balsam is used. We have now 

 Protococcus mounted in Gum Thus which is of good 

 color and refractive index, showing the organisms 

 nicely. I have tried this mode with BacillariacesB (Diato- 

 macese) and found it all that can be wished for. Vege- 

 table and animal tissues can be mounted in it also and I 

 think that we have in it just the medium we wanted. 



