In article <1995Jun16.134129.17490 at galileo.cc.rochester.edu>
ttha at uhura.cc.rochester.edu (Tom Thatcher) writes:
>> I think I answered most of this already. I want to correct a
> misconception, though, it that cells do not move to their location,
> as you seem to suggest, rather, location determines fate (mostly).
> A newly divided cell in the embryo's tail doesn't think to itself,
> "I'm a brain cell, better get a move on."
>I think that cellular movement is an important component of
development. Certainly in the cellular slime mold, Dictyostelium and
relatives, cellular movement is an important determinant in
differentiation and development. The fate of the individual cell,
whether stalk or spore, is determined by the timing of its movement
from the free-living amoeba stage into the multicellular animal, the
grex or slug.
Animal embryologists could also supply examples of cellular movement
during development. Certainly the flat fish, e.g. flounders, provide
excellent examples of final form being the result of cellular, indeed
entire organ, movement. The embryonic fish and early free-swimming
stages are vertical fish with the eyes on two sides of the body. Later
development results in the migration of the eyes putting both on the
same side of the body. The fish now swims on its side and rests
sideways on the ocean floor.
David H. Griffin
Department of Environmental & Forest Biology
College of Environmental Science and Forestry
350 Illick Hall
One Forestry Drive
Syracuse NY 13210-2788
e-mail: griffin at mailbox.syr.edu