Echinoderms including sea urchins are widely distributed in Philippine waters (Domantay 1968; Alcala 1976;
Celis 1982). Several species of sea urchins including Tripneusces gracilla, Diadema setosum and Echinomecra machaei thrive in the coastal waters of Ta/in Bay, Lian, Batangas (Geronimo 1984). Their density, diversity and standing crop, (Godinez 1982) trophic niche (Pinto 1981) and growth patterns (Ga"ido et al. 1988) have been partly described. The use of sea urchins as biological materials for embryological and ecotoxicological investigations has been demonstrated in earlier studies (Okubo and Okubo 1962; Kobayashi 1 971, 1984; Gaudice 1973; Lonning and Hagstrom l 975a; Dinnel et al. 1982; Ozrecic and Krajnovic 1984; Spinelli and Albanese 1990). These studies had provided the basis for pursuing similar investigations at the De La Salle University Marine Biological Station (DLSU-MBS). Sea urchins are available in Talin Bay during most parts of the year, are easy to collect and to acclimate to laboratory conditions. Their gametes and embryos are amenable to simple laboratory rearing experimentation. Results of initial investigations on the fertilization and early development of T. grati//a, D. setosum, and E. mathaei provided the basis for the establishment of their respective developmental time table. This paper reports the developmental time cable established for T. grati//a. Similar reports on D. setosum and E. mathaei will appear in future publications.