Much like the basic tapeworm, planaria use the muscles of the body wall to move along. The muscles are located in two main layers, both just beneath the epidermis of the organism. The outer layer is composed of circular muscles. The second layer is composed of horizontal muscles. Finally, there is sometimes a third layer which is composed of diagonal muscles. When all of the muscle layers work together and contract, it results in undulations of the body margin which help to move planaria forward.
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