20 Dr. & the Rev. S, Graham Brade-Birks— 
Dr. Edgar Newbery, now Professor of Physical Chemistry in 
the University of Capetown, was kind enough to expose 
- centipedes from Kent, which were luminous when tested in 
other ways, to the action of Radium, no luminosity of the 
animals was produced. Moreover, if luminosity was caused 
by the presence of radioactive substances, could the animals 
control the appearance of light? Perhaps they could control 
the chemical production of a temporary screen. ven so, 
why should luminosity die away so rapidly under all known 
circumstances in its artificial production? There are some 
questions here for physicists to settle. At any rate, we can 
safely conclude that the light 1 is not due to the ‘bombardment 
of a permanent “screen” in the sternal region ‘by ‘the dis- 
[Barge of a radioactive substance in the exeretion of ee 
“white glands.” And also that, if a temporary “ screen’ 
produced, it is the result of chemical action, in which the 
excretion from the “ white glands ” takes a part. 
Crystallization. 
When G. carpophagus is electrically stimulated under 
water luminescence is induced much in the same manner as 
in air. Therefore crystallization, as Dubois (8) meant it, 
is not the cause of luminosity in this species at any rate. 
We have not yet proved that liquid crystals .are. absent. 
The experiment of inducing phosphorescence below water 
also throws some doubt upon the conclusion of Dubois that 
crystallization was the cause of the phenomenon in Orya 
barbarica. Moreover, we shall observe almost immediately 
in the present study that crystallization takes place in the 
mucin excreted by the ventral surface of non-luminous 
ceutipedes. 
Change of State. 
The breakdown without chemical: action of the solid 
contents of a gland to form a liquid would absorb energy 
and not emit it. 
Other Physical Possibilities. 
In the consideration of any purely physical cause, similar 
objections are likely to present themselves. It would appear 
that new substances must be formed before physical phe- 
nomena exhibit themselves, and we are forced back upon 
the conclusion that no purely physical cause which we have 
investigated seems adequate to explain the production of light 
by Geophilus carpophagus. 
