By analyzing the examples from fairytales and epics , we can get two single stories and the inferior type of this theme and by studying the arrangement of the story from the order of the plot , we can get four mechanisms of development : multiple starting points ; reoccurrence ; heterozygosis and branch expansion , which explain the inherent principle for a continual development and super length of the story 從神話、史詩中搜集到的該類型的例證,分析可得該主題下的兩類單體故事以及更次一級的型式類別,并在情節(jié)序列上考察目連救母故事的組構(gòu)情況,總結(jié)得出“復(fù)合起點” 、 “反復(fù)再現(xiàn)” 、 “異型融合”和“旁支擴張”四種生長機制,以期從一個側(cè)面說明該故事持續(xù)生長并構(gòu)成超長篇規(guī)模的內(nèi)在原理。