HISTOLOGY OF THE LIGHT ORGANS. II 
is a layer of highly insoluble material, which, as already mentioned, is called 
the “reflecting layer.” The light is generated in the glandular material, 
the ‘‘driisenkorper,”’ d. K., and passes through the funnel-shaped opening, 
finally emerging through the lens, /, into the air. 
S IIT. Transverse section of Photinus pyralis (dia- 
™ / gramumatic). 
Rot isee—-R ‘The right-hand half shows the arrangement and 
‘ distribution of the trachex, while the left-hand 
half shows the modification of the luminous 
S tissue at the point of attachment of the breath- 
ing muscles. 
G, testes; I, intestine; L, true photogenic tissue; 
R, reflecting layer; S, spiracle or stigmatum; 
L Sp, spiral organs (function uncertain); T, 
main trachez to photogenic organ; Tb, main 
respiratory trachez; M, muscle fibers. 
Fic. 4. 
This description seems a little fantastic, for optically the system is 
extremely inefficient. ‘The low reflecting power which must obtain in the 
so-called ‘reflecting layer’’ and the roundabout way for the light to reach 
A, Section through the ventral region of a fish, Maurolicus 
pennanti. 
B, Section through alight organofafish. (After Mangold.) 
Fic. 5. 
the lens (granting that the lens and the reflector have sufficient figure to give 
directive power) does not carry conviction to the idea that this is a miniature 
