296 PHILOSOPHY OF ZOOLOGY. 
There is one signal addressed to the eye, apparently em- 
ployed by many to express certain feelings ;_ but with whose 
characters we are imperfectly acquainted. TI here allude to 
luminousness or phosphorescence. It has been observed of 
the common glow-worm, that the females, which possess 
this luminous power in a much greater degree than the 
males, are destitute of wings; and, therefore, incapable of 
flying about in search of a mate; but that during the sea- 
son of love, when the light is emitted in greatest brilliancy, 
she is able to guide her vagrant lover to her presence. By 
some it has been supposed, that this luminous property is 
destined to direct the animals possessed of it, with greater 
certainty to their prey. But it is obvious that it would 
warn the objects of their pursuit, if animated, of their ap- 
proach, and facilitate the efforts of their fces to discover 
their retreat. 
We come now to consider the artificial or acquired signs: 
addressed to the eye. This method of holding intercourse 
between the individuals of a species, appears to be peculiar 
to the human race, and to be the instrument by which man 
can gain possession of the information of past generations, 
and be able to record the transactions of the present time, 
for the benefit of future ages. 
If we consider a person in a barbarous state of society, 
anxious to communicate intelligence to his tribe, respecting 
an animal which he had observed in the woods, unlike to 
any in size and shape which he had ever seen, we are not 
aware of any other means which he could employ to accom- 
plish his object, but to draw its figure upon the sand, or 
scratch its outline upon the rock. ‘This figure being diffi- 
cult or tedious to execute, would be abridged in the course 
of frequent repetition, until it became a symbol merely, in- 
stead of a picture, to represent the animal in question. If 
a particular name was bestowed upon the animal, then the 
