part of part of immediately preceded by immediately preceded by occurrent stage 8 late swimming blastula stage very late blastula stage The embryo is composed of about 800 cells and is surrounded by a fertilization envelope. The wall of the embryo is thinner and smoother than at previous stages. The vegetal plate has not formed. Many cells are ciliated but the embryo has not begun to rotate within the fertilization envelope. Note for euechinoid indirect developers: molecular labeling typically indicates the presence of 32 large micromere descendants and 4 small micromere descendants at this stage. ecao_developmental_stage vLB