Invertebrates The Crayfish 
her great nippers and the two pairs of walking feet, 
also armed with nippers, she loads up as much as she 
can carry between her great claws and her breast. 
She keeps her load from overflowing by holding it 
down with her first pair of jaw-feet, just as I have seen 
a schoolboy use his chin, when carrying a too large 
load of books in his arms; and she keeps the load 
from falling out by supporting it from beneath with 
her first pair of walking legs. Thus, she starts off 
with her ‘“‘apron’’ full, walking on three pairs of feet, 
until she gets to the dumping place; then she sud- 
denly lets go and at the same time her tail straightens 
out with a gesture which says plainly, ‘‘There!”’ 
Sometimes when she gets a very large load, she uses 
her second pair of walking legs to hold up the burden, 
and crawls off successfully, if not with ease, on two 
pairs of legs,—a most unnatural quadruped. 
HOUSE 
The aquarium in which the crayfish is kept should 
have at least three inches of gravel at the bottom, 
and there should be in it an abundance of pond weed. 
However, the water should not be more than three or 
four inches deep above the gravel, and at one side the 
gravel should be slanted up until it is within an inch 
or so of the surface of the water. Not more than two 
or three crayfish should be kept in an ordinary 
aquarium. 
FOOD 
Bits of meat, liver, or fish attached to a string, so 
that they may be removed before too stale, should be 
placed in the aquarium two or three times a week. 
Professor George Embody has trained his crayfish to 
eat various kinds of fish food made from meat scrap. 
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