Notes on Mi/ri(iiiO(I(C. 17 



L cation. 



Our first enquiry must be : What is the exact seat of 

 liiiiiiiiosity ill G. C(irjjoj)h(i(/us? 



In some of our earlier experiments we found that an 

 excretion on to the vential surface of the body caused the 

 li'^ht iu this s[)eeies, and the examination of specimens 

 ventrally under the microscope showed that opaque rounded 

 masses of material Mere often present under the pure-tieUi 

 and under the surfaces of the plates known as 2y3 and 27 

 {^g. 2). We know now that these white rounded masses arc 

 ijroups of pyriforni and probably unicellular gland.s intimately 

 associated with the production of light (PI. I. fig. 9 and PI. 11. 

 fig. 11). When we stimulated specimens provided with these 

 ghinds in a holder under the microscope in the dark, so that 

 we could observe the production of light by the animal, we 

 found that soon after the ai)|)lication of the stimulus tliere 

 was a sudden rush of light filling in tiie grooves behind the 

 sternite and around the outer edges of the plates 2/3 and 27, 

 and also filling in the grooves between these plati s and the 

 sternite itself (PI. 1. fig. 10). AVhen the centipedes were ex- 

 amined subsequently in direct light, it was found that the 

 " white glands ^■' of the stimulated segments had disappeared 

 cither entirely or almost entirely (Pi. II. figs. 11 & 12). 

 Thus, luminosity in Geo})hilus car[)0[)hagus is entirely ventrnl 

 in incidence and is accompanied by the discharge of the 

 " white glands." 



The luminous material in G. carpophagus is a viscous 

 fiuid, practically colourless, with a characteristic fruity 

 odour not unlike that of some decaying flowers, drying 

 raj)idly in air, and strongly acid in its reaction. 



IJy means of a partial illumination (PI, 1. fig. 8), instead of 

 woikiug ;ib.solutely in the dark, we were able to observe the 

 incidence of luminosity with greater accui'acy and also to 

 watch the behaviour of the " white glands " upon stimula- 

 tion. The amount of illumination employed in such experi- 

 ments should l)e just sufficient to make the outlines of the 

 " white glands '^ distinguishable under the microscope. \Ve 

 found that immediately upon a muscular cuntraetion of the 

 body and the discharge of the ''white glands" to the ex- 

 terior luminosity is produced, and in one case the expulsion 

 of their contents was suilieiently slow to admit of u)orc 

 detailed ol)servation. On electrical stimulation the opaque 

 patches (contents of the " white glands") ui.der the posterior 

 part of the sternite were seen to move instantaneously 

 Ann. di: Mag. N. JJid. Sci. i). Vol. v. 2 



