The number, distribution and morphology of the supramedullary neurons are investigated in two genera of Teleosts belonging to the same family (Labridae). The supramedullary neurons of the two genera (Crenilabrus and Coris) differ in number, size and cytological aspect; these morphological disagreements may be due to a different functional activity.
In the oviparous Teleost, Jordanella floridae, the Reissner fibre is early formed by the generalized secretory activity of the cells lining the ventricles. Subsequently the secretory activity becomes restricted to the subcommissural organ and the Reissner fibre is connected only with this structure. In Jordanella there is no secretory activity of the flexural organ. This finding differs from the data found in Gambusia (viviparous fish of the same suborder of Teleosts) and may be due to a different...
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