28 SCIENCE SKETCHES. 
this dark color often extends on the back part of 
the body, so that the fish looks as if he had been 
taken by the tail and dipped into a bottle of ink. 
But with the end of the nuptial season, this color 
disappears, and the fish regains his normal strawy 
hue. 
The head in Boleosoma resembles that of Dzple- 
ston ; but the habit of leaning forward over a stone, 
resting on the front fins, gives a physiognomy even 
more frog-like. His actions are, however, rather 
bird-like; for he will strike attitudes like a tufted 
titmouse, and he flies rather than swims through 
the water. He will, with much perseverance, push 
his body between a plant and the side of the aqua- 
rium, and balance himself on the slender stem. 
Crouching cat-like before a snail-shell, he will snap 
off the horns which the unlucky owner pushes tim- 
idly out. But he is often less dainty, and seizing 
the animal by the head, he dashes the shell against 
the glass or a stone until he pulls the body out or 
breaks the shell. Boly, alas! is the “ Quaker of 
our aquarium ” only in appearance. 
Gayest of all the darters, and indeed the gaudiest 
of all fresh-water fishes, is the Rainbow Darter 
(Pecilichthys ceruleus Storer). This is a little fish, 
never more than three inches long, and usually 
about two. Everywhere, throughout the northern 
parts of the Mississippi Valley, it makes its home 
in the ripples and shallows of the rivers and in the 
shady retreats of all the little brooks. The male 
fish is greenish above, with darker blotches, and 
its sides are variegated with oblique bands alter- 
nately of indigo-blue and deep orange, the orange 
