Notes on the Podura Scale . By Alfred Letherby. 399 
Again, if these results are produced by a fluid substance, how is it 
that the larger scales fail to display these characteristics ? I regard 
the smaller scales as of more delicate construction than the larger 
ones, and therefore more easily ruptured. 
These are points an explanation of which may reasonably be 
demanded of those inclined to regard these appearances as having 
been produced by the presence of foreign matter. 
The photographs were taken with a Powell and Lealand 1/12 
apo. obj. N.A. 1 ‘40. Powell and Lealand apo. condenser N.A. 1*40. 
Reichert’s compensating ocs. 8 and 18. Critical illumination with 
paraffin lamp. Aplanatic cone of condenser used N.A. * 80, Approxi- 
mate diameters x 900, x 1000, x 2000. 
2 d 2 
