Fig. 5

Eusyllis blomstrandi. Schematic representation of the segmental distribution and intensity of light emission in an early (a), middle (b), and late flash (c) of a series in a posterior fragment identical with that shown in Figs. 4 and 6. A square unit represents one segment (vertical axis) and a time interval of 10 ms (horizontal axis). The numbers on the ordinate left and right of the graphs in this figure and in Figs. 6, 7, 9, and 10 symbolize the positions of the individual segments in the trunk in an anterior–posterior (left) and in a posterior–anterior (right) direction. A numbering from the posterior end towards the anterior is included because the light pulses may start from the posterior-most segment (Fig. 10), and because the total number of luminescing segments may increase in subsequent flashes towards the anterior, such that the posterior-most segment may become the point of reference. By estimating the light intensities seen in the original video images, like those in Figs. 4 and 8, three categories of emission intensities are symbolized in the graphs by plotting manually three grades of shading, from dim light (heavy shade) to full light intensity (no shade), as shown in a representing the original video images of Fig. 4