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Fig. 6. Angular rotation of 1-day-old (neural tube stage) embryos of red-eyed
treefrogs in the 5 min after moving them to different initial positions within
the egg. Grey background indicates egg surface covered by other eggs and leaf
substrate; white background represents air exposure and zone of higher
perivitelline oxygen levels. Experimental embryos positioned with their
developing head at the hypoxic rear of the egg moved it toward the air-exposed
surface (A,B), whereas controls positioned with their developing head at the
front of the egg remained there (C,D). Data are means ± s.e.m.;
N=25 embryos per treatment.