1. Conant, F. S., Mem. Biol. Lab. Johns Hopkins Univ., 4, 1 (1898).
2. Okada, Y. K., Bull. Biol. France Belg., 61, 241 (1927).
3. Chapman, D. M., in Symp. Zool. Soc. London (edit. by Rees, W. R.), 16 (Academic Press, London, 1966),
4. Thiel, Hj., in Symp. Zool. Soc. London (edit. by Rees, W. R.), 16 (Academic Press, London, 1966).
5. Uchida, T., Bull. Mar. Biol. Stat. Asamushi, Tôhoku Univ., 13, 247 (1969).