The hypophysis of the marine teleost fish, Mugil auratus Risso.

Owing to its lack of a hypophysial stalk, the hypophysis of the marine fish, Mugil auratus, is of the platybasic type. Its differentiation into adenohypophysial and neurohypophysial regions well conforms with the situation already recognized in other fishes. But, although the adenohypophysis shows distinction into pro-, meso- and meta-adenophypophysis, the lineo-vertical arrangement which they assume is not of common occurrence. By contrast, the neurohypophysis forms the usual central nervous core, surrounded by the adenohypophysial regions. The acidophils constituting the pro-adenohypophysis, having a deep staining affinity, resemble those in the meso-adenohypophysial region. The acidophils of the meso-adenohypophysis occupy a small region, whereas their associating cyanophils occupy a larger ventral region. The meta-adenohypophysis consists of an integral convoluted sac of epithelial amphiphilic cells. Such encloses the bulk of the neurohypophysis. It is remarkable that the neurohypophysial fibres never interdigitate among the meta-adenohypophysial cells, so they are more closely related in arrangement to tetrapods than to fishes.