The difference on morphological characters of Mactra veneriformis with two inner-shell colors and associated pedigrees selection were studied by using the method of path analysis and random mating among individuals. It was showed that the difference on morphological characters of M. veneriformis with two inner-shell colors was not significant （P〉0.05） except for their colors. In both, the correlativity were all significant for all four characters （P〈0.01）, but the mean morphological characters that effect body weight were different. The correlation index （R2） of morphological characters on live body weight were all larger than 0.85, which indicated that these characters were the key traits for body weight. There was no significant difference on D larvae and at days 3 between two pedigrees （P〉0.05）, but the shell length of purple pedigree was larger than the other （P〈0.01） at days 6, 12 and 15. The difference on survival rate between two pedigrees was not significant （P〉0.05）, but the hatching rate and metamorphic rate of purple pedigree was higher than that of white pedigree （P〈0.01）. At nursing stage, the shell length of white pedigree was larger than that of purple pedigree （P〈0.01）. However, the variation between two pedigrees was decreased during the outdoor period, and it was no difference at days 90 finally. Accordingly, there was no significant difference on growth rate and survival rate at nursing and grown-out stages （P〉0.05）.%采用通径分析原理及个体间随机交配的方法，进行了两种壳内色四角蛤蜊的形态性状差异及品系选育研究。结果表明，两种壳内色四角蛤蜊除颜色不同外，其它形态性状间无显著差异（P〉0．05）；两者的4个数量性状之间的相关系数均达到极显著水平（P〈0．01），但影响重量性状的主要形态性状并不相同；壳形态性状对活体重的相关指数均大于0．85，表明所选的壳形态性状是影响活体重的重点性状。两个品系D型及3日龄幼虫大小无显著差异（P〉0．05），6、12和15日龄紫色品系的壳长和生长速度均高于白色品系，差异极显著（P〈0．01）；幼虫期间，两者的存活率无显著性差异（P〉0．05），但紫色品系的孵化率和变态率明显高于白色品系（P〈0．01）。稚贝室内培育期间，白色品系的壳长明显大于紫色品系（P〈0．01）；但室外养成期间，两者差异逐渐缩小，90曰龄两者壳长已无显著性差异（P〉0．05）；稚贝期间两者的生长速度及成活率均无显著性差异（P〉0．05）。
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