24. Dr. & the Rev. S. Graham Brade-Birks— 
In G. carpophagus, then, more than one type of gland 
is present, and one of these has been shown to excrete a 
substance almost certainly esseutial for the production of the 
animal’s light, . 
Thus upon such stimulation as resuits in the ordinary 
production of light there are present on the ventral surface 
of the body : the contents of the white glands ; and, almost 
certainly, always the contents of at least one other type of 
gland ; and air, with its ordinary impurities including water- 
vapour. We do not kuow enough of the chemical nature of 
the contents of the individual glands yet to speak confidently, 
but we can at least conclude that in the excretion which 
accompanies luminosity there are generally present: (i.) the 
Fig. 16, 
Enlarged view of some glands of the same section, x 160. 
Lettering as in fig. 15. H. K. B.-B. del. 
contents of the white glands; for these we propose the 
name of protoluciferin *, (11.) mucin, (iii.) acid. The last two 
may, or may not, be produced by the same gland, and in 
either case protoluciferin may, or may not, contain acid 
as well. 
We may now examine more closely, from the chemical 
point of view, the conditions and incidence of luminosity in 
G. carpophagus. 
* Lucifertn, the name proposed by Dubois for the luminous fluid he 
met with in Orya barbarica, includes the whole excretion of the ventral 
surface and probably includes mucin and an acid, apart from any sub- 
stance corresponding to our protoluciferin. 
