Bivariate phase analysis of isolated body parts. These data are the same as shown in Figure 4. The left column shows phase comparisons for BG-luc; cry+ (plotted with asterisk) vs tim-luc; cry+ (plotted with open circles). The right column shows BG-luc; cry+ (plotted as asterisk) vs. BG-luc; cryb (plotted as open circles). The axes for each plot describe an x-y plane with the origin occurring at the center of the unit circle plotted within the plane for reference. The point (0,1) defines the beginning of the subjective day, or time 0. Time moves in a counter clock-wise direction on this circle. Each point denotes the head of a vector that summarizes the phase of an individual specimen. The tail of this vector would extend from the origin to the plotted point, with the direction indicating the mean peak time across cycles and the magnitude (distance from the origin) describing the variability of the peaks for each specimen. However, these tails are not plotted to simplify the appearance of the figure. A mean vector is calculated and fully plotted to show the mean phase time for each group of points as well as the mean variability (indicated by its length). Below each plot: the length of each mean vector is given by r; the mean time of each vector is given by phi and the p-value used to assess whether the phase differs between groups is obtained by Hotelling's two-sample test (for more detail see ). This analysis is continued in Figure 10.