Miscellaneous. 415 



black- or plumbeous-coloured forms, examples of which I have seen 

 from Men tone. 



Olivaceus, var. nov. 



Various shades of olive-green. Figured by Pollonera (op. cit.). 

 I have examined specimens from Mentone. 



Flavo-griseus, var. nov. 



Yellowish grey. Foot-fringe usually lighter than the body. 

 From ^iTentone. 



It is difficult to separate some forms of olivaceus from this 

 variety. 



On the MecJidnism of the Production of Liglit in Orya barbarica 

 of Algeria. By M. Raphael Dubois. 



The discovery of the photogenous faculty in the Algerian Orya 

 barbarica, is of relatively recent date. This fine Geophilid was 

 observed for the first time, in a luminous condition, almost at the 

 same moment by M. Raphael Blan chard at El Kantara (April 

 1888) and by M. J. Gazagnaire at Nemours (May 1888). 



Moreover, a certain number of important peculiarities were 

 mentioned by M. Gazaignaire * ; the phosphorescent substance is 

 exuded from pores situated upon the sternal and episternal plates in 

 the form of a viscid yellowish fluid, with an odour sui generis, 

 drying rapidly on exposure to the air and insoluble in alcohol. 



In September 1887, on observing some specimens of ScoUoplanes 

 crassipes which had been sent to me from La Fere (Aisue) by 

 M. Huet, I had myself remarked that the luminous fluid was 

 excreted from the ventral surface of the body, contrary to an opinion 

 which I had previously advanced ; but I had not published this 

 observation, since I intended to complete it later on. As I was 

 unable to obtain fresh examples of ScoUoplanes, I went to Algeria 

 to look for specimens of Orya barbarica. 



Not only have I verified the accuracy of the facts recorded by 

 M. Gazagnaire, but I have been able especially, thanks to the 

 employment of the microscope, of which this investigator did not 

 avail himself, to make new observations which confirm in the most 

 precise manner the correctness of the definitive theory of the 

 mechanism of the production of light, as set forth in my last work 

 on Pholas dactylus f. 



The facts which I have already recorded in various communica- 

 tions are correct, but their interpretation has sometimes varied in 

 consequence of new discoveries ; to-day, however, uncertainty can 

 no longer exist, owing to the facility for observation and experiment 



• J. Gazagnaire, " La phospliorescence ehez les Myriopodes " (Bulletin 

 de 1ft Socit'te Zodlogiquo ae France, t. xiii. p. 182). 



t K. Dubois, ' Anatomie et Physiologie comparc^es de la Pkolade dactyli'.' 

 Paris, G. Masson, 1892. 



