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Abstract
The present study deals with the cranial nerves of the bony fishs, Tilapia Zillii. The results obtained can be summarized as follows:
1- The nervus olfactorius arises from the sensory cells as separate bundles. It leaves the nasal capsule through the foramen olfactorium advehens and enters the cranial cavity through the foramen olfactorium evehens. It runs for a long distance in the orbital region.
2- The nervus olfactorius enters a sessile bulb, there is no olfactory tract or olfactory peduncle.
3- The optic nerves enter the cranial cavity through one and the same foramen. They cross each other under mesencephalon with the right verve dorsal to the left one forming a complete deccussation.
4- The nervus oculomotorius leaves the cranial cavity through its own foramen and divides into rami superior and inferior. it carries pure somatic motor fibers as well as parasympathetic the radix ciliaris longa forming a common ciliary root.
5- The ciliary ganglion has sympathetic root. There is only one ciliary nerve arising from the ciliary ganglion.
6-The nervus trochlearis passes outside the cranial cavity through its own foramen. It has no connection with the other cranial nerves. It carries pure somatic motor fibers.
7- The nervus trigeminus arises by one root. It leaves the cranial cavity through the prootic foramen together with the anterodorsal and the anteroventral lateral line nerves.