In 1964, Levin and Bang discovered that gram-negative bacterial endotoxin could rapidly induce gelation of Limulus amebocyte lysate. This observation has led to the development of the most sensitive and specific method for the detection of bacterial endotoxin in pharmaceuticals and drugs intended for human use. Over 10 years ago, Bang injected endotoxin into young horseshoe crabs and observed a time and dose-dependent coagulation of the whole hemolymph. Limunectin, LEBP-PI, and Limulus CRP are found together with coagulin as part of the hemolymph clot at the time of endotoxin-induced exocytosis of amebocytes. In this manner, these molecules with agglutinin/lectin activities could work in concert to assist in the recognition and eventual removal of invading microorganisms from the circulating system. Although the mechanism of endotoxin-induced clot formation is to a large extent understood, the mechanism of clot dissolution and removal in the Limulus hemolymph remains to be clarified.