THE GLOWWORM'S LIGHT-EMITTING APPARATUS. 317 
The faculty of producing light is very tenacious ; but agents 
which destroy organic tissue annihilate it, e.g. } undiluted mi- 
neral acids and caustic alkalies, strong alcohol, ether, organic 
acids, and a powerful electric stream. Nerve- 'paralyzing nar- 
cotics distinctly weaken it, e. g., coniin and prussic acid. In 
from three to five minutes the light disappeared from insects 
exposed to prussic acid vapour, and in ten minutes the function 
was so destroyed as to be incapable of re-animation by any 
stimuli. 
Insects that have been dried up recover their illuminating 
power when moistened with water, and frozen insects revive 
by the warmth of the hand. 
The persistent irritability of the light-organ, and its power 
of continuous luminosity, are astonishing. In a moist atmo- 
sphere excised farts may continue to give light for twenty-four 
to thirty-six hours : the longest observed time was forty-eight 
hours ! The power of illumination failed in one to three hours 
when the insect was immersed in water. 
Experiments with Du Bois Raymond's apparatus showed 
that the insect, when shining brightly, deflected the needle 
from three to seven degrees. 
From the researches here recounted Kolliker concludes : — 
First, that the light-organ is a nerve apparatus, and finds its 
nearest analogy in the electric organ of fishes, since in both 
cases the same nerve stimuli excite, and nerve sedatives 
paralyze, functional activity. Secondly, that the hypothesis of 
oxidation of phosphorus is disproved by facts. Thirdly, that 
the metamorphosis of the albuminous contents of the cells is 
an accompaniment and material source of light function, the 
urate of ammonia crystals found in the white greasy cells 
being one of the residual products of the tissue change, and 
proportionate in quantity to the amount of change, which 
in its turn is regulated by the controlling influence of nerve 
force. 
W e may now compare the account of Professor Kolliker with 
those of other authors, both of earlier and more recent dates. 
De Geer, Treviranus, and Oarus, have noticed distinct and 
sometimes brilliant light both in the larva and pupa. The 
writer has found that the two small ovoid masses which may 
be dissected from the body of the pupa to be formed of a 
thick and tough capsule (see fig. 1), inclosing contents so 
opaque that nothing further could be distinguished under the 
microscope than a closely aggregated mass of granular par- 
ticles. But on tearing up the capsule with needles these 
particles, under a higher power, proved to be nuclei, which 
showed in a few instances a cell membrane slightly raised from 
the nucleus. These were therefore the parenchyma cells of 
z 2 
