Fig. 11. Development of (A) V₃ and (B) V₄. To compare the data from fish of different length (i–iv), we calculated an electrogenic index: the electromotive force divided by the length (expressed as a percentage of the fish length) of the generating region. In all fish, there is a head-to-tail progressive increment of the electrogenic index with percentage of fish length. Note that both the maximum amplitude and the slope of the curves of both waveform components increase as fish grow. The increase of the growth coefficient for V₄ is larger than for V₃.