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Microtome for cutting
ultrathin tissue sections
Panulirus interruptus,
the California spiny lobster
Stomatogastric
ganglion
Synaptic contacts
within a small region
of nervous tissue
Shape of one nerve cell
(in lobster stomatogastric ganglion)
Reconstructing cell shape from sections
Drosophila melanogaster, the laboratory fruit fly
Thorax
Abdomen
Head
the cardia in the fly digestive tract
Elaboration of cardia structure,
along the main line of fly evolution
“Giant” nerve fibers ( )
in cross section of fly nerve cord
*
Giant fibers conduct
signals from antennae
to flight muscles.
Drosophila
melanogaster
Muscina
pascuorum
Minettia
magna
Tipulidae, Tipula bicornis Forbes
Lauxaniidae, Minettia magna (Coquillett)
Tabanidae, Tabanus calens Linnaeus
Syrphidae, Helophilus fasciatus Walker
Fly species differ in
their distributions of
nerve-fiber diameter.
Bombyliidae, Sparnopolius sp.
Bombyliidae, Poecilanthrax sp.
How can evolution
adjust the properties
of individual nerve
cells?
One point which has greatly troubled me; . . .
what the devil determines each particular
variation? What makes a tuft of feathers come
on a cocks head, or moss on a moss rose?
Charles Darwin
Letter to T.H. Huxley 1859