18 Dr. & the Rev. S. Graham Brade-Birks— © 
posteriorly, as along a potential canal (like a bottle-neck) 
opening into the groove behind the sternite beneath its 
posterior edge and so posterio-dorsal to it. Then almost 
simultaneously with this squirt-like movement, but never- 
theless a very small fraction of a second later, luminescence 
began and was seen along the posterior edge of the sternite 
and around the edges of the episternal plates 28 and 2y¥. 
We therefore conclude that the contents of the “ white glands” 
are almost certainly essential for the production of light in 
Geophilus carpophagus. 
The different groups of “ white glands ”’ of the same seg- 
meut are separately controlled, for it is sometimes seen that 
the sternal ‘“‘ white glands” are discharged apart from any 
expulsion of material from those of the episternal plates. 
After the discharge of the “ white glands” the secretion 
slowly accumulates again until opaque patches of glands are 
once more visible in the sternal and episternal regions. The 
‘“‘ white glands” of a luminous Darwen specimen, which we 
diagnosed as G. carpophagus ¢, with 51 pairs of legs, 
collected 14. vii. 1919, were mostly discharged by electrical 
stimulation the same day. Little or no change was obser- 
vable on the 19th of July, when the animal was provided 
with soil, but by the 7th of August there was a considerable 
recovery. ‘Unfortunately this animal escaped through an 
error in connection with an experiment performed later. 
Incidence. 
Is it due to parasitic or symbiotic micro-organisms ? 
Our next enquiry must be: Are we dealing here with 
light-production by micro-organisms in symbiotic or patho- 
genic relationship with the lumincus Geophilid, or are we 
dealing with an entirely chemico-physicai phenomenon ? 
In one of our dissections a white gland was observed 
under the high power of tle microscope to be filled with 
minute particles agitated by Brownian movement, a move- 
ment which was evidently closely paralleled by the .ex- 
perience of Dubois (6) already quoted in ‘the case of the 
jelly-fish, Hippopodius gleba. In our case the particles were 
of considerable size, being visible through the cell-wall and 
without an oil-immersion lens. 
Before the discovery of luminous Geophilomorphs in 
Lancashire we attempted: to culture lummous micro- 
organisms from light-producing centipedes sent to us from 
Kent, but without success, but in the case of Geophilus 
