1450 Journal of Applied Microscopy 



A Rapid Method of Making Slides of Amoeba. 



If a small film of detritus which contains abundant amoebae be placed in a 

 solid watch glass with plenty of water and examined with a magnification of Id 

 to '10 diameters, amoeba; can, after a little practice, be readily seen and can be 

 picked out with a thin-walled dipping tube such as any one can readily make for 

 himself. The medicine droppers which one buys have walls too thick to be 

 available. 



The drop of water containing the amoeba may be placed on a coverslip and 

 with a little care any fragments of dirt taken up with it can be removed to a dis- 

 tance by needles and then taken away altogether by a cloth or a bit of filter 

 paper. With a little experience also it will be easy so to manipulate the cur- 

 rents as to bring the amoeba to the center of the slide. As much water should 

 be drawn off as is possible without incurring the risk of allowing the animal to 

 dry. After he has been quiet for a few moments and has begun to put forth his 

 pseud opodia, he adheres slightly to the glass and it is now possible by a sudden 

 move to drain off the rest of the water and to replace it by a small drop of picric 

 alcohol (saturated solution of picric acid in 50 per cent, alcohol). If the alcohol 

 is placed directly upon him and is not allowed to fall from any considerable 

 height, the attachment to the glass will not be loosened. The cover may now be 

 inclined somewhat and a gentle current of 50 per cent, alcohol allowed to flow 

 over it until the amoeba appears quite colorless. Dehydration may be accom- 

 plished by allowing two or three c.c. of each of the higher grades of alcohol to 

 flow over it in the same way. This done, the animal may be permanently fixed 

 to the cover, as Overton suggests, by adding a small drop of a very dilute solution 

 of collodion, which, by tilting the slip in various directions, may be spread out 

 into the thinnest possible film. As soon as the collodion ceases to flow it may 

 be completely hardened by dropping the cover, amoeba-side up of course, into 

 80 per cent, alcohol. 



In this alcohol the preparation may be left as long as convenient, or it may 

 at once be stained with any suitable stain, such as borax carmin or haematoxylin. 

 I am accustomed to use Syracuse watch-glasses for manipulation of such covers, 

 and the only precaution necessary is to incline the cover somewhat as it is put 

 into a fluid, since if attention is not given to this point the entire film with the 

 specimen may float away. 



The collodion, like the amoeba, will of course be colored, but if the film was 

 not too thick it may be entirely decolorized before the color is withdrawn from 

 the specimen. In dehydrating, amylic alcohol, which does not dissolve collo- 

 dion, should be substituted for the ordinary absolute ethyl alcohol. If the speci- 

 men is so large that supports are needed for the cover, two slips of paper pre- 

 viously soaked in xylol may be used instead of wax feet. The final step is of 

 course to place a drop of balsam upon a slide and invert the cover upon it. 



Although the process may sound somewhat tedious, it is really a rapid one. I 

 have repe<itedly put away a completed specimen in my cabinet less than half an 

 hour from the time when the amoeba was crawling about in his home. I should 

 add that I have not made any cytological study of specimens prepared in this 

 way. For purposes of demonstration, however, they are exceedingly satisfactory. 



Wellesley College. M. A. WiLLCOX. 



