A "NORMAL" DEVELOPMENT OF DENUDED EGGS OF THE STARFISH, ASTERINA PECTINIFERA.

Experimental conditions that allow "normal" development of starfish eggs stripped of the fertilization membrane are reported in this paper. Four kinds of intercellular relation are distinguished during the pre-hatching stages of these eggs. Cells from 2- to 8-cell stages are hardly related to each other, while those from 16- to 128-cell stages are bound loosely together. After the 8th division (about 5.5 hr after insemination at 21°C) cells adhere closely and cooperate with each other to perform morphogenetic movement of "blastulation". This relation is taken over by that of a true multicellular system at about 10 hr after insemination. Closely after this, the function of cilia carries the embryo away from the substratum.