he anatomical and histological observations of the brain in fishes differ among species, but they resemble each others in the number of brain compartments, and it is necessary to characterize well the anatomical and histological observations in the brain of each particular kind of fishes for doing further subjects in the brain. Five brain divisions usually observed which are from cranial to caudal; telencephalon or forebrain (contain 2 olfactory lobes and cerebrum), diencephalon (contain epithalamus, thalamus and hypothalamus), mesencephalon or midbrain (contain 2 optic lobes which are connected internally with torus longitudinalis and medially with the torus semi-circularis, and optic tegmentum),
metencephalon or hindbrain (cerebellum) and myelencephalon or brain stem (medulla oblongata). The ventricular organization composed of the olfactory, lateral, the third, the tectal and the fourth ventricles.
The adult neurogenesis process is usually observed in the fish brain, unlike mammal's brain. The adult neurogenesis usually detected in cerebellum, optic lobe, and telencephalon.