22 SCIENCE SKETCHES. 
tion in this Centennial year, for he is altogether an 
American product. He has all that ardent desire 
for perfect freedom that is supposed to be native 
to this continent. Unless all appearance of cap- 
tivity be concealed in a well-kept aquarium, he 
will quickly lie on the bottom, dead. Here, at 
the beginning (for much as we may regret the 
fact, the death of some individual must precede 
our acquaintance with the group, and even to some 
extent with the individual himself), we observe 
two noteworthy facts: the fish in dying does not 
turn over, and does not rise to the surface. On 
dissection, we find that the air-bladder is only 
rudimentary, being structurally, but not function- 
ally, present,—a distinction not without meaning 
in these days of evolutionary hypotheses. If our 
tank be so arranged that the conditions are nearly 
natural, there being an abundance of stones and 
weeds on the bottom, our Johnnies will cheerfully 
live with us, and we shall be ready to study their 
individual peculiarities, or, as Boyesen’s “ Scientific 
Vagabond” would have said, their “ psychology.” 
For it must be known that while all fish are fish, 
they are so only as all men are men. The chil- 
dren of one family are not more unlike one another 
than the fishes of one brood might be if the sickly 
ones and the lazy ones were as carefully guarded 
as are ours. As it is, they have their individuality. 
One is constantly darting over and among the 
stones, never resting, moving his head from side 
to side when his body is for a moment still. An- 
other will lie for hours motionless under a stone, 
moving only for a few inches when pushed out 
