52 CEYSTALS AND LIVING UNITS 



covering-glass was placed, and then a simple cement (proved to be 

 harmless) was run round its edge leaving only a minute aperture — 

 so as almost to prevent evaporation. The account given in 

 " The Beginnings of Life " (Vol. I., p. 295) of the observations then 

 made is as follows : — 



" Mounted in the manner above mentioned, it is not difficult — 

 with the stage of the microscope in a horizontal position — to bring 

 into the field of view a portion of the film, which either contains 

 no visible particles, or only a small number, such as can be easily 

 counted.' With the slip resting on one of Strieker's hot-water 

 plates maintained at a temperature of 85°-95° F., it may be found 

 that, in the course of three or four hours, faint and ill-defined 

 whitish specks, less than ^Tj-Jinr" in diameter, make their appearance 

 pretty evenly dispersed throughout the field of view. These are 

 at first almost motionless — exhibiting only the merest vibrations, 

 but no progressive movements. They gradually become more 

 distinct, assume a sharper outline, and after a variable time some 

 of them develop into distinct Bacteria. At first they exhibit gentle 

 oscillations and tremblings only, though gradually they display the ■ 

 more characteristic darting movements. The study of the mode 

 of origin of these primordial living forms is, indeed, facilitated 

 and rendered much more certain by the fact that they remain 

 comparatively motionless for a long time after their first 

 appearance, and also continue faint and much less refractive than 

 when in the more mature condition. Hence it becomes a matter 

 of the greatest ease to watch their appearance in thin films of 

 fluid, and also to distinguish them from other extraneous particles 

 with which they may coexist." 



I have recently adopted a simpler method for making observa- 

 tions of this land, doing away with the necessity for any apparatus ; 

 and have used an infusion of turnip or one prepared from a small 

 portion of fresh beef or mutton, which was subsequently filtered 

 through two layers of the finest Swedish paper. A drop of one of 

 these fluids is allowed to fall on a cleaned microscope slip, over 

 which a ^ of an inch square cover-glass is placed, and the excess 

 of fluid is then removed by bringing a piece of blotting-paper to 

 its edge. It is well to see that one or njpre minute air bubbles 

 exist somewhere in the film before applying some melted paraffin 

 wax round the edge of the cover-glass." A small speck of paint 



' Working with a magnifying power of 1,000 diameters. 

 " I have used wax which melts at 103° F. 



