EXPERIMENTS WITH COCKROACHES
1.
Cockroaches
are excellent
experimental animals, of which
the common species (periplaneta americana)
becomes active,
soon after dark each day
& scavenges
continuously for five of six hours.
2.
But clever Janet
Harker, of Cambridge
University
found out, that if
one has its
head cut off, then it
no longer shows this
circadian rhythm of activity. |