Fig. 10. Cells intercalate mediolaterally in both the wild-type and ntl mutant embryo (A,B), but only during brief intervals in the mutant, when compared with the wild type (C). (A) Intercalating cells become neighbors (blue, neighbor gains), pushing apart old neighbors (red, neighbor losses). Hence, for cells undergoing MIB, neighbor gains are ML (horizontal in the diagram) and neighbor losses AP (vertical; see also Fig. 2). (B) The polar plots show that these predicted behaviors are observed; the distributions are evidently broadened for the mutant. All four distributions are nonrandom (P<0.05; Watson's U²_n test). The distributions are based on 623 gains and 633 losses for the wild type, and 1473 gains and 1822 losses for the mutant. (C) Colored bars show the durations of time periods when neighbor gains and losses are significantly oriented along any axis (Watson's test for nonrandom data). In the wild type, these periods of highly oriented activity are sustained during most of the time interval sampled. In the mutant, pulses of oriented and random behaviors are interspersed.

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