Boyal Microscopical Society. 195 



in condenser and iris diaphragm, and I used also monochromatie 

 light. 



Now with regard to the reality of these appearances, I think 

 the evidence is in their favour, inasmuch as with direct hght a good 

 Ath or ith objective shows a distinct series of lines between, and 

 parallel to, the ribs on the upper surface of the Lepisma scale, 

 while very careful examination with transmitted hght resolves these 

 Hues into Podura-like markings. 



Experience has taught me to distrust appearances in the micro- 

 scope seen by transmitted light alone ; but of course where there is 

 any corroboration from the use of direct hght, it gives a propor- 

 tionate value to examinations by high powers. These examinations 

 are hable to all kinds of errors, and the results claimed cannot be 

 too rigidly scrutinized. I give my observations for what they are 

 worth ; they are certainly curious, and may not be without use in 

 calling attention to a not over easy object for testing the perform- 

 ances of modern high-power objectives. 



I must just say a word about the parallel ribs being beaded 

 more or less; they certainly show as such by reflected light, but 

 not by transmitted light, except at the portions projecting beyond 

 the end of the scale, where the rib certainly seems to taper off in 

 beading. 



Q 2 



