The Magnetic Sense — The Living Compass

Passage outline

Supporting details

The existence of the earth magnet and the invention of the navigating compass

◇Our earth is a big magnet and a little freely (71)   ▲ 

  magnetic needle lines itself with the earth magnet to point north and south.

◇(72)   ▲   on the idea above, the navigating compass was invented.

The possibility of birds’ built-in compasses

◇ One piece of evidence is the (73)   ▲    of many birds between their summer homes and winter homes.

◇ Birds can recognize star patterns on clear nights and keep on course (74)   ▲     under cloudy skies 

The  (75)   ▲     on pigeons’ and bees’ built-in compasses

◇Little magnets were tied to the pigeons’ heads to (76)   ▲     their magnetic sense.

◇The pigeons’ magnetic sense seemed to be affected on (77)   ▲    days.

◇Similar things with the same results were done with bees.

The  (78)   ▲     of the magnetic stuff for the animal compass

◇Little rod-like bacteria were found by chance to swim together in the direction of (79)   ▲    .

◇Some animals had a chain of dense magnetic particles in or close to the (80)   ▲     inside their bodies.