The presence of complement-like activity in the humoral fluid of amphioxus was examined . the complement classical pathway ( cp ) activity is assayed by determining the amount of serum required to hemolyse a given number of sensitized sheep red blood cells ( srbc ), whereas the complement alternative pathway ( ap ) activity measured in the same manner, but by using rabbit red blood cells ( rarbc ) instead of sensitized srbc 文昌魚體液可溶解懸浮在10mmollegta-mg-gvb緩沖液中的正常的兔血紅細(xì)胞、綿羊紅細(xì)胞、及部分哺乳動(dòng)物、鳥類、兩棲類和魚類的代表動(dòng)物的血紅細(xì)胞;而在gvb~(2+)緩沖液中時(shí)對(duì)抗體包被的綿羊紅細(xì)胞卻沒有溶血活性。