III ON ANIMAL LIFE 93 
much greater brilliance, and in these cases the 
glow seems to be a real love-light, like the 
lamp of Hero. 
Many small marine animals, Medusa, 
Crustacea, Worms, ete., are also brilliantly 
luminous .at night. Deep-sea animals are 
endowed also in many cases with special 
luminous organs, to which I shall refer 
again, 
SENSE OF DIRECTION 
It has been supposed that animals possess 
also what has been called a Sense of Direc- 
tion. Many interesting cases are on record of 
animals finding their way home after being 
taken a considerable distance. To account 
for this fact it has been suggested that 
animals possess a sense with which we are 
not endowed, or of which, at any rate, we 
possess only a trace. The homing instinct of 
the pigeon has also been ascribed to the same 
faculty. My brother. Alfred, however, who 
has paid much attention to pigeons, informs 
me that they are never taken any great dis- 
