THE GLOWWORM'S LIGHT-EMITTING APPARATUS. 
325 
electricity be possible in a creature of sucb simple organization, 
there can scarcely be any difficulty in recognizing the delicate 
nerve and cell apparatus of the glowworm as sufficient for a 
more complicated function. 
In conclusion, we must briefly allude to that which has been 
called the volitional control of the insect over its production of 
light. The highest development of insect brain and nerve must 
necessarily be limited to instinctive acts and reflex function. 
There can be neither intellectual operation ( design ) nor percep- 
tion where there is no material organ of will or mental percep- 
tion. All insects perform the functions proper to their species, 
in the same manner, under the same circumstances, and with 
the same results, whether that result be the best calculated for 
the purpose or not — -just as any given animal. tissue must go 
through the phase of inflammation after injury, without any 
intention of cure ; and the cure may or may not follow. The 
gradual improvement of nerve or muscle function is the conse- 
quence not of experience, but of continual development of the 
organism and its collective vitality. The light-producing func- 
tion, so different from all others that it may justly be considered 
“ sui generis," is obviously not performed for the individual 
benefit of the insect, but for the facilitation of the most im- 
portant act of its life — the reproduction of the species, and 
fecundation of the female. But the sexual purpose effected by 
this means, one beyond the knowledge or experience of the 
insect, is an appointed phase of its existence, placed beyond 
its option by an instinct implanted in all brute nature by the 
Creator. 
EXPLANATION OF PLATE. 
Fig. 1. Rudimentary light-organ of Lampyris, consisting of a thick, tough 
capsular envelope, and densely-packed nuclear contents. 
„ 2. “ Fatty bodies,” forming the common interstitial substance of the 
abdominal cavity. These bodies appear strung together upon fila- 
ments which connect them in a loose, net-like omental tissue. The 
connecting filaments are continuous with the transparent struc- 
tureless envelope which surrounds each small mass of granular 
refractive greasy substance. * 
„ 3. Development of “ fatty bodies.” Along the median line of the back 
are attached a series of thread-like septa, which pass to the sides of 
the abdomen. Between these the fatty bodies first appear as large 
cells, filled with a clear substance, and containing large nuclei. 
