mourn, Now in| Loyal Microscopical Society. 3 253 
doubtless for the purpose of protecting the body of the insect from 
damp or injury; in order to do both the one and the other, two 
things are necessary: firstly, that it should be strong; and secondly, 
that the external surface should be smooth. Both these require- 
ments are fulfilled in those families of this group provided with 
scales; whether we take Lepisma, Petrobius, Tomocerus, Temple- 
tonia, Beckia, Setra, Lepidocyrtus, or Degeeria, the structure of all 
is on the same type, although in appearance so different. 
The wpper or external surface is only slightly ribbed as in 
Lepisma, or mottled or undulated as in the other families, whilst 
in all the wnder surface is corrugated or strengthened by longi- 
tudinal bars or ribs running from the base to the apex of the scale. 
Experiment fully bears out this statement, and anyone may try 
it for himself as follows :— 
Place the insect from which the scales are to be obtained on a 
piece of velvet, and gently press a slip of glass, we will call it 
No. 1, upon it; the scales will be shed on the under surface of the 
glass, and the surface adhering to the glass will be the upper or 
outside surface of the scale. Having obtained a number of scales 
upon No. 1, place a glass No. 2 upon No. 1, and press them 
together; some of the scales on No. 1 will adhere to glass No. 2. 
The surface adhering to glass No. 2 will be the under or inside 
surface of the scale, or that part next the body of the insect. 
Treat both these glasses exactly alike; place each in turn on 
the stage of the microscope, adjust the object-glass, and breathe 
gently on the slide. The scales on No. 1 will exhibit a wonderful 
and most beautiful phenomenon; the moisture from the breath 
dropping on the scales will run up the furrows in it, and in drying 
return with the greatest precision, no running across the scale, no 
irregularity of action, but steadily up and down. ‘The scales on 
No. 2 glass, on being treated in the same manner, present, on the 
contrary, a very different appearance ; the moisture collects on the 
exposed surface of the scale in minute globules, and when drying 
off spreads evenly over the whole surface of the scale, without any 
apparent direction being given to it by unevenness in the structure 
of the scale, save an indication of a slightly undulated surface. 
But can this experimental appearance be made to coincide with 
the apparent structure as seen under the microscope? how about 
notes of interrogation, beaded structure, &c.? I am prepared to 
assert that it is easily explained, but my present object is to call 
attention to the mode of ascertaining structure, and to suggest the 
plan to others, at the same time confidently to assert that the two 
surfaces of these scales are dissimilar, the upper or outer surface 
being nearly flat, the under or inner being furnished with ribs or 
bars, varying in number and running from the base to the apex of 
the scale. 
