Comparative morphology of the visual system of some Japanese species of Soricoidea (Superfamily) in relation to leif habits.

In some species of Japanese Soricoidea, Sorex shinto, Mogera wogura wogura, Mogera wogura kobeae, Dymecodon pilirostris, and Urotrichus talpoides, the cytoarchitecture of the eyeball and its accessory organs, the dorsal lateral geniculate nucleus, the superior colliculus, the lateral posterior nucleus of the thalamus and the visual cortex were investigated in correlation with life habits. In Sorex, living preominantly on the ground, there is a duct-like palpebral fissure, and most of the parts of the visual system are well developed in adaptation to its life habits. In the almost completely fossorial moles, no palpebral fissure is recognized, and the visual system is less developed owing to adaptation to their habits. In the semifossorial shrew-moles. Dymecodon and Urotrichus, the features of the eyeball and the visual system in the brain are intermediate between those of the Sorex and Mogera group. Furthermore, taking account of the visual system of certain species from other orders, it is assumed that the cytoarchitecture of the visual system is dependent more upon the ecological niche than on systematics.