18 Dr. & tlie l^ev. S. Graliam Brade-Birks— 



posteriorly, as alonp; 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 

 simnltaiiconsly with this sqniit-like movement, but never- 

 theU?S3 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 2y3 and 27. 

 We therefore conclude that the contents of the " white glands " 

 are almost certainty essential for the production of light in 

 Geophilus carpoj)liagns. 



The difl'erent groups of " white glands " of the same seg- 

 ment 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 e|)isternal 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 e[)isternal regions. The 

 " white glands^' of a luiuinons Darwen s])ecimen, which we 

 diagnosed as G. carpojihagus ? , 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. Uu fortunately this animal escaped through an 

 error in connection with au experiment performed later. 



Incidence. 



m 



Is it due to parasitic or stjnibiotic 7nicro-organisms ? 



Our next enquiry must be: Are we dealing here with 

 light-production by micro-organisms in symbiotic or ]Kitlio- 

 genic relationship w ith the luminous Geophilid, or are we 

 dealing with an entirely chemico-pliysical i)henomenon ? 



In one of our dissections a white gland Avas observed 

 nnder the high })ower of the microscope to be filled w ith 

 minute j)artieks agitated by Brownian movement, a move- 

 ment- which was evidently closely paralleled by the ex- 

 perienee of Dubois (6) already quoted in the case of the 

 jelly-fisli, Hippojiodius glchu. In our ease the particles were 

 of consi(leial)le size, heing visihle through the cell-wall and 

 witiiout an oil-imnuM'sion lens. 



Ik'lure tlie dise(*very of luminous Geopliilomor])hs in 

 Lan(-asliire we attempted to culture luminous micro- 

 organisms from light-producing centiifcdcs sent to us from 

 Kent, but wilhtnit success, htit in the ease of Genphihis 



