Notes on Myriapoda. 11 
that the physiological process is here independent of the 
organ. 
In the case of another piece of research (6) on luminosity, 
Dubois raises several points of special interest to us in the 
present study. He shows that in Hippopodius gleba, a 
transparent animal of the Hydrozoan family of the Poly- 
phyide, the ectoderm in certain places becomes milky and 
opaque on mechanical stimulation, owing to the immediate 
production of a multitude of granules deposited in the 
protoplasm of the ectodermal cells, a production accompanied 
at night by the emission of light. The chemical composition 
of these granules is very complex, they are neither fat nor 
ammonium urate. Dubois considered that each of these 
granules contained a little vacuole at its centre. In the 
luminous cells these granules (vacuolids) were seen to have 
very complex movements, and their absolute independence in 
the midst of the plasma was such that it might be supposed 
to be due, he thought, to parasitic micro-organisms; but the 
attempts of Dubois at culture in various media met with no 
success, and he concluded that micro-organisms were not 
the cau<e in this case. 
Dubois (8) in a much later paper, not considered by 
Verhoeff (12) in the summaries to which we have already 
referred, tells us that Orya barbarica was seen in a luminous 
state for the first time in 1888 in North Africa, that Gazag- 
naire found that a phosphorescent substance was excreted 
by pores cpening upon the sternal and episternal plates, that 
this substance was a viscous fluid, yellowish with an odour 
sui generis, insoluble in alcohol, drying rapidly in air. 
Dubois himself found that a luminous fluid was excreted 
by the ventral surface of the body in Scolioplanes crassipes. 
Dubois says that in Orya barbarica the luminous substance 
is found in unicellular, pyriform, hypodermic glands, 0 08- 
0-10 mm. x 0°05-0'06 mm. In stained sections’ he saw 
“‘ gouttelettes ” in the granular glandular protoplasm; these 
‘* gouttelettes ” were round to ovoid in shape and were also 
observed in the secretion—they were not fat, but exhibited 
the histo-chemical characters of protoplasm or condensed 
albuminoids. In the centre of each of these “ gouttelettes,” 
immediately after their contact with air, Dubois saw a very 
refringent spot ; these corpuscles, which he states occur in 
all luminous organs, then had the form to which he gave 
the name of vacuolid (see also 7). The refringent point 
became the centre of a crystal or group of crystals. Dubois 
stated that both air and water are necessary for luminescence, 
