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第四章扁形动物门一、门的主要特征１．身体扁平，具两侧对称的体型。两侧对称（又称左右对称）是指通过身体的中轴（从口面到反口面），只有一个对称面可将身体分成相等的两部分。两侧对称的体型对动物进化有着极其重要的意义：两侧对称的动物，其身体均有明显的前后、左...
Chapter IV The Main Characteristics of the Doors and Gates of the Flat Animal 1. The body is flat and has a symmetrical body shape. Symmetry on both sides (also known as bilateral symmetry) refers to the central axis of the body (from the oral surface to the opposite surface), and only one symmetry plane can divide the body into two equal parts. The symmetry between the two sides of the body has an extremely important significance for the evolution of animals: bilateral symmetry of the animal, the body has obvious front and back, left ...