[Comparative analysis of the neuronal and synaptic organization of the mesencephalic visual center of Greek and steppe turtles].

The stratification, neuronal structure and synaptic organization of tectum opticum have been studied in two species of tortoises (Testudo graeca and Testudo horsfieldi, Gray) by means of Golgi methods and electron microscopy. The midbrain tectum in these closely related animals has some common properties, but at the same time it possesses certain species specific features. Their properties in common appear to be connected with the common ecology and closely systematic place of Testudo graeca and Testudo horsfieldi. The specific features appear to be connected with the species differences in visual behavior of these species.