Ascidian eggs do not respond to parthenogenetic activation. However they can develop gynogenetically: after entering the egg, the sperm-nucleus was removed with a small portion of cytoplasm by fragmentation, and the gynogenetic fragment was followed through development. In many cases the fragments cleave with the typical pattern, gastrulate and finally give rise to normal larvae: in a percentage of cases, however, the fragments cleave with a radial pattern, do not gastrulate and give rise not to larvae but only to undifferentiated permanent blastulae.