760 BE. A. MINCHIN. 
form or general structure,’ so that no ill-effects result from 
the use of the stain, while the microscopic image is rendered 
much sharper and clearer. 
My method of carrying out investigations upon the effects 
of technique was the following: Preparations of Try pano- 
soma lewisi were fixed and stained in various suitable 
ways, and the results were all drawn with the camera lucida 
at a magnification estimated at 3000 diameters, and are 
reproduced in this memoir at the same scale. It is possible 
that the figure 5000 is not perfectly accurate, but if not, it 
makes no difference to the result, since the object was to 
compare the effects of the methods employed, and for purposes 
of comparison the exact magnification is immaterial, provided 
it be uniform throughont. All the drawings given here were 
executed using always the same microscope and length of 
tube, the same lenses, camera lucida, drawing board and 
illumination. Some of them were done by me, but most of 
them by my assistant, Miss Rhodes, to whom my best thanks 
are due for her skilful help. Zeiss’s apochromatic objective 
2 mm., 1°40 aperture, was used, combined with compensating 
oculars. ‘lhe source of illumination was the flame of an oil 
lamp placed edgeways, and concentrated by a Zeiss collecting 
lens, through a monochromatic screen on to the mirror of the 
microscope, and thence reflected through a centring achro- 
matic condenser of Zeiss. This illumination, if properly 
arranged and focussed, gives very perfect definition—a very 
important point in studying these preparations; I have 
frequently found that structures had been overlooked which 
became visible with improved illumination. I frequently 
compared the results obtained in this way with those given 
by a monochromatic illuminating apparatus set up with a 
prism in such a way that any part of the spectrum could be 
used, in order to obtain confirmation of the structures as 
drawn with the illumination described. 
' A slight vacuolation, which is probably an artefact, makes its 
appearance near the kinetonucleus after treatment with methyl-green 
(figs. 5-8). 
