134 PROCEEDINGS OF THE SOCIETY. 



introduced into the cell by the flowing water. With some kinds of 

 organisms there would, of course, be no such danger, but it would 

 hardly be safe with an Amoeba, for instance. He had himself found, 

 when studying the life-history of minute species, that it answered 

 very well to make a small cell of ordinary thin glass, and by 

 surrounding the whole with blotting-paper, kept constantly wet, he 

 had been able to retain three or four monads of large size under con- 

 stant observation for several weeks. A similar arrangement to that 

 adopted by Mr. White had been used on the human body as a means 

 of applying evaporating lotions. 



Mr. J. W. Stephenson said he had brought for exhibition some 

 scales of insects [MacMlis maritimus and Tomocertus \Podura\ plumhea), 

 mounted in phosphorus, and shown under a oV'ii^ch objective with 

 very oblique light and the binocular. They demonstrated that it was 

 possible even with such a high power to get with the binocular a 

 distinctly stereoscopic effect, and that when so seen a much more 

 perfect idea of the structure of the scale could be obtained than was 

 possible under the monocular. Although the structure of the scales 

 of Machilis maritimus and Tomocertus plumhea is probably the same, 

 they cannot be said to be " corrugated " in either case. In Machilis 

 the appearance of the upper side is that of longitudinal semi-cylin- 

 drical grooves, which had been likened by a medical gentleman to a 

 pill machine ; whilst the latter, probably from being so much smaller, 

 appears to have rectangular grooves, similar to those in a curry-comb, 

 the back being in each case supported by slender transverse bars, 

 which are approximately from one-third to one-half the distance 

 apart of the longitudinal divisions. 



Mr. Beck said that as to the Podura scale shown by Mr. Stephen- 

 son, what he described with respect to the structui'e of the scales was 

 entirely opposed to what they had been shown to be. In such 

 matters where high powers and oblique light were used, he thought 

 it was very doubtful if they ought to believe what they saw, as they 

 might so very easily be deceived by appearances. So far as he knew, 

 no one had hitherto brought forward anything which would refute 

 what he had shown some years ago, when he put moisture on one side 

 of a scale, and found that it dried off quite flat, whilst if he put some 

 on the other side, it ran up and down as if in corrugations. His 

 brother also did the same kind of thing with a Lepisma scale and 

 Canada balsam. Moisture, as they knew, would get into slides which 

 were mounted dry, and the same appearances were presented there. 

 Having kept the insects, and being able to tell which was the upper, 

 and which the under side of the. scale, and being also able to show 

 these corrugations in a mechanical way, he could only say that even 

 if the effect could be seen as described by Mr. Stephenson, he should 

 not, he was afraid, be convinced, for he knew very well that in most 

 cases, by reversing the shadows, they could reverse the appearances. 

 If they wanted to determine the real structure with high powers, they 

 must argue from analogy rather than from what they saw. They had 

 compound substances to deal with, and effects were produced which 



