1. Parpart, A. K., in Primitive Motile Systems in Cell Biology (edit. by Allen, R. D., and Kamiya, N.) (Academic Press, New York and London, 1964).
2. Scott, A., Biol. Bull., 119, 260 (1960).
3. Dan, K., Embryologia, 2, 115 (1954).
4. Belanger, A. M., & Rustad, R. C., Biol. Bull., 139, 415 (1970).
5. Morgan, T. H., Anat. Am., 9, 141 (1893).