JOURNAL 
OF THE 
ROYAL MICROSCOPICAL SOCIETY. 
AUGUST 1895. 
TRANSACTIONS OF THE SOCIETY. 
IX . — Notes on the Podura Scale. 
By Alfred Letherby, F.R.M.S. 
( Read lltli April , 1895.) 
[With additions.] 
Plate VII. 
The photographs on plate VII. are intended to demonstrate the 
existence of two membranes : 
One a delicate hyaline membrane from which the stalk extends ; 
and 
One a denser (optically) brownish membrane superimposed upon 
the other. 
The latter is perforated all over in the form known as exclamation 
marks. 
It is not easy to suspect the existence of these perforations when 
examining a perfect scale ; hut when portions of the darker membrane 
have been removed (by accident or otherwise), a postage-stamp fracture 
is readily seen. This fracture is a strong presumptive proof of the 
perforation. 
The photographs show scales with portions of the upper mem- 
brane removed, and on one in the centre of the scale (figs. 1 and 4) 
is a small portion partly dislodged. The shadows on one side of 
the scales are as clearly indicated as in the perfect specimen. On the 
reverse side there is a marked absence of these shadows. It is also 
worthy of notice that when the darker membrane is entirely absent 
EXPLANATION OF PLATE VII. 
Fig. 1.— X 950. 
„ 2 and 3.— x 1000. 
„ 4. — Same as fig. 1, slightly different focus. X 900. 
„ 5. — Scale with exclamation marks absent. X 2000. 
„ 6.— x 2000. 
,, 7. — X 2000. Larger scale broken across, exhibited to show entire absence of 
any indication of spines or separate scales where exclamation marks are. 
2 D 
1895 
