1.前言生物进化和生物退化是物种在客观生存条件下的一种现象。种的数量增多,其分布区扩大,该物种则进化;种的数量减少,其分布区开始分散並进一步缩小,该物种则退化。生物进化是与物种适应能力分不开的,鱼类的新性发育是个体发育早期阶段的一种非常重要的适应性,它对物种进化来说,即增加种或种群的数量来说有着巨大的意义。 1. Introduction Biological evolution and biological degradation are species under the objective existence of a phenomenon. The number of species increased, their distribution expanded, and the species evolved; the number of species decreased, their distribution began to disperse and further narrow, and the species degenerated. Biological evolution is inseparable from the ability of species to adapt. The new development of fish is a very important adaptation in the early stages of the development of an individual. It has a huge impact on the evolution of species, that is, increasing the number of species or populations Meaning.