We purified two hatching enzymes, namely high choriolytic enzyme (HCE; EC ) and low choriolytic enzyme (LCE; EC ), from the hatching liquid ofFundulus heteroclitus, which were named FundulusHCE (FHCE) and FundulusLCE (FLCE). FHCE swelled the inner layer of egg envelope, and FLCE completely digested the FHCE-swollen envelope.