PROGRESS OF MICROSCOPICAL SCIENCE. 
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animals, why should not the “ scales ” also be covered with like 
structures ? As it is my belief at the present time that in the Test 
Podura scale, as well as that of the Degeeria, the structure of hair and 
scale is alike, I will give the points which have caused this opinion. 
There is no doubt that the epithelial scales on the hairs of L. curvi- 
collis and Degeeria domestica bear a great similarity to the markings 
on the scales themselves. They are of the same shape, and I have in 
several instances made measurements which showed the coincidence 
in size between the “spines” on the hairs and those of the scales. It 
is comparatively easy to obtain isolated spines from the hairs, and 
these, when viewed by central illumination, present, as I have stated, 
an appearance identical with the so-called spines of the scales. If 
unilateral illumination be employed, a beading is also seen on the 
spines separated from the hairs, although I have never been able to 
produce the “ varicosities ” as well as when they were attached to and 
lying upon the hair itself. Having satisfied myself as to this fact, the 
nest thing to do was to separate the spines from the scales. I acci- 
dentally came into possession of a slide of Degeeria domestica scales, 
mounted by J. Beck, of London, I believe. Here, on this slide, I 
perceived to my great satisfaction a fractured scale, which showed the 
spines projecting beyond the broken edge, some of them bent and dis- 
torted, and what were evidently places from which others were torn. 
At a short distance from the broken scale I beheld isolated spines just 
like those on the scale, the measurements of which corresponded to 
the size of those attached to the scale. These separate spines I have 
repeatedly seen as rows of beads when unilateral illumination was 
resorted to, and the projecting spines from the broken margin of the 
scale exhibited the beading under similar conditions. Dr. J. J. "Wood- 
ward, of the Army Medical Museum, Washington, on receiving from 
me some photo-micrographs that I made of the appearances with 
central light, wrote me that he was of opinion that the free spines 
came from some of the compound hairs that might be upon the slide. 
Now, even granting this to be so, the projecting spines, their being 
beaded under oblique light, the beading of the free spines, seem to 
point to the fact that there is something yet to be accounted for that 
the theory of beads leaves untouched. This, then, represents the 
state of the case and conclusions which I incorporated in my paper 
nearly a year ago. Since then I have secured some specimens of 
Degeeria, and continued my experiments, — imperfectly, it is true, as 
time could not be spared for exhaustive research in this direction. I 
selected specimens of scales that were not mixed with hairs, and that 
showed no free spines, and, placing these in such a manner that the 
discharge from a Leyden jar could be brought to bear uj)on them, not 
only tore to pieces the scales, but scattered the spines far and wide. 
Again, by means of crushing in a small agate mortar, and even on the 
slide itself, by pushing about the covering glass with the handle of a 
dissecting needle, I have fractured a scale in such a manner that the 
spines lay free and side by side with the broken scale. What more 
is wanting to show that hairs and scales are of a similar structure ? — 
the hair consisting of a shaft, upon the surface or exterior of which 
