Notes vn ^f^/riapo(l(t. 11 



that the physiological process is here independent of the 



or<fan. 



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 (jleba, a 

 transparent animal of the Hvdrozoan family of the Polv- 

 phyidje, the ectoderm in certain i)hices 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, bethought, to parasitic micro-organisms; but the 

 attempts of Dubois at culture in various media met wiih no 

 success, and he concluded that micro-organisms Avere not 

 the cause in this case. 



Dubois (8) in a much later paper, not considered by 

 Verhoeff (i2) 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 opening 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 Scol'wplanes crussipeft. 

 Dubois says that in Orya barbarica the luminous substance 

 is found in unicellular, pyriform, hypodermic glands, 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 

 tlie histo-chemical characters of protoplasm or comlensed 

 albuminoids. In the centre of each of these ''gouttelettes," 

 immediately after their contact with air, Dubois saw a very 

 refringent spot ; these corpuscles, wliich he states occur in 

 all luminous organs, then had the form to wliich 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, 



