A new method of removing the membranes from ascidian eggs in the mass is described. Essentially the method is the use of proteolytic enzymes. The development of isolated blastomeres is described, confirming Conklin's results that the development of each is strictly partial and that the whole development is a mosaic. It is also shown that the presence of the egg membrane and of injured or dead blastomeres in his experiments in no way invalidated those results.