Notes on Myriapoda. 25 
Upon stimulation, under the usual circumstances, mucin, 
acid, and protoluciferin are excreted upou the ventral surface 
of the animal’s body into contact with one another and 
the air with its impurities, and immediately luminosity is 
produced. 
If the discharge be dried luminosity ceases, but upon the 
addition of water it is continued ; so that water is essential 
to the production of light in Geophilus carpophagus. 
It should be noted that water will be present in the 
excretions themselves as a normal constituent of mucin. 
It has generally been accepted in other similar cases that 
atmospheric oxygen was essential to the production of light. 
It has already been mentioned that G. carpophagus can be 
stimulated to luminesce under water, but atmospheric oxygen 
might in that case be present, in solution, in the tracheze of 
the animal’s body, or as a film on the surface of the body 
itself. ‘To obviate all these factors a newly made film was 
introduced into a vessel of water, at the ordinary temperature, 
boiled previously and so free from dissolved air. Lumino- 
sity was not inhibited, but continued normally below the 
surface of the water. Therefore, atmospheric oxygen is not 
essential for the production of light in the case of Geophilus 
carpophagus. 
A similar experiment, perhaps less convincing, but con- 
firmatory, was conducted with the substitution of olive-oil 
for boiled water. Luminosity agai continued below the 
surface of the oil. With alcohol the excretion was coagu- 
lated and the luminosity was inhibited almost instantaneously. 
As an outcome of these enquiries, we can add that, a the 
case of Geophilus carpophagus, under certain conditions all 
the essentials for the production of light are secreted by the 
animal itself, and upon the expulsion of these essentials to 
the exteriur the chemical action which appears to take place 
in the excretion is accompanied by the production of light. 
The Use of Phosphorescence. 
When we come to consider the utility of light-production 
in the economy of the life of G. carpophagus, we are face to 
face with no mean problem, Future work may provide an 
adequate solution, but at present we have little but sugges- 
tion to offer. 
Misleading Factors. 
In approaching this question scientifically there are some 
