202 Prof. Wagner’s Observations on 
held at a distance from the eye, and which had been preserved 
for three years, I observed the candle encircled with three 
beautiful concentric rings, red on the inside and green with- 
out. ‘Phese colours were no doubt those of mixed plates. 
In examining the lamin of the crystalline lens under the 
microscope, we are often perplexed with a variety of colours 
apparently spread over the surface of the plate. These co- 
lours are not the effect of chromatic aberration, but arise from 
the interference of the coloured pencils produced by the two 
surfaces of the laminze. If we take a thin lamina, and, hold- 
ing it opposite to a candle, look at its surface with a lens 
about an inch in focus, we shall see the whole of it covered 
with the most brilliant and varied colours, not inferior to 
those of the richest opal. These colours vary as we incline 
the laminz in a plane cutting the fibres of it perpendicularly; 
and when the portion of the lamina is flat, they form a series 
of rectilineal serrated fringes perpendicular to the direction 
of the fibres. When the portion of the lamina is much curved, 
the fringes are irregular, and form, occasionally, returning 
curves of every variety of form and of every imaginable tint. 
If we immerse one of the surfaces of the lamina in a fluid of 
the same refractive power, we remove, as it were, the fibrous 
structure of ihat surface, and the serrated fringes immediately 
disappear. ‘This observation led me to imitate these fringes 
by combining two series of grooves cut on the surface of se- 
arate strips of glass*. The effects were precisely similar 
and highly beautiful; and in the prosecution of the subject 
I was led to the observation of a series of very curious phz- 
nomena, which will form the subject of a separate communi- 
cation. 
XXXIX. Observations on ‘the Compound Eyes of Insects. 
By Rupotew Waener, Professor in Erlangen.t+ 
O* examining the works of Jehn Miiller on the Eyes of 
Insects, with a view to the 2nd Part of my Manual of 
Comparative Anatomy, I have only been able, as might be 
expected, to confirm the greater part of his statements. But 
with respect to the very interesting structure of the compound 
eye I have arrived at a different opinion. Strauss, indeed, 
represents small knob-shaped, or rather cup-shaped, ganglions 
of the fibres of the optic nerve, which Miller and Duges 
* These phenomena are much more splendid, when the grooves are 
formed upon thin plates of isinglass, by taking an impression of them front 
a steel surface, 
+ From Wiegmann’s Archiv fiir Naturgeschichte, 3° Heft, 1835; com- 
wunicated by Mr. William Francis, Berlin. 
