1. 1) M. J. Wells: Brain and behaviour in Cephalopods, Stanford University Press, Stanford, 1962, p. 171.
2. 2) T. Hara: Photosensitive pigments in cephalopod retina. Zool. Mag., 77, 99-108 (1968) (in Japanese).
3. 3) H. Inada and M. Ogura: Historical changes of fishing light and its operation in squid jigging fisheries. Rep. Tokyo Univ. Fish., 24, 189-207 (1988) (in Japanese).
4. 4) T. Okutani: Useful and latent cuttlefish and squids of the world, National Cooperative Association of Squid Processors for the 15th Anniversary of its Foundation, Tokyo, 1980, pp. 2-6.
5. 5) S. Duke-Elder: The eye in evolution, Henry Kimpton, London, 1958, p. 144.