Habits.—Does the crawfish walk better in water or out of it? Why? Does it use the legs with the large claws to assist in walking? Do the swimmerets (under the abdomen) move fast or slow? (Observe it from below in a large jar of clear water.) What propels it backward? Forward? Does the crawfish move at a more uniform rate when swimming backward or forward? Why? In which way can it swim more rapidly? Do the big legs with claws offer more resistance to the water while it is swimming backward or forward? How does it hold the tail after the stroke, while it is darting backward through the water? Hold a crawfish with its tail submerged and its head up. Can the tail strike the water with much force? Allow it to grasp a pencil: can it sustain its own weight by its grip?
Feeding.—Offer several kinds of food to a crawfish that has not been alarmed or teased. Does it prefer bread, meat, or vegetables? How does it get the food to its mouth? Does it eat rapidly or slowly? Does it tear the food with the big pincers? Can it gnaw with the small appendages near the mouth?
Breathing.—Does the crawfish breathe with gills or lungs? Place a few drops of ink near the base of the hind legs of a crawfish resting quietly in shallow water. Where is the ink drawn in? Where does it come out? To explain the cause and purpose of this motion, place a crawfish in a large glass jar containing water, and see the vibratory motion of the parts under the front portion of the body. There is a gill paddle, or gill bailer, under the shell on each side of the body that moves at the same rate.
Senses.—Crawfish are best caught with a piece of meat or beef's liver tied to a string. Do they always lose hold as soon as they are lifted above the water? What do you
