Flatworms are primarily known as flatworms. These flatworms are bilaterally symmetrical and are triploblastic. Flatworms are also acoelomates and participate in gas exchange through diffusion in the integument layer. Flatworms are divided into two classes; Trematodes and Cestoidea. Clonorchis sinensis, a trematode parasite, and Echinococcus granulosus, a cestoid parasite, are similar in that both are flatworms, but these parasites differ in terms of their life cycle and ability to cause infections in humans. Clonorchis sinensis belongs to the Trematoda class. All trematodes are parasites. Most trematodes have complex life cycles, normally having two or more hosts, of which the first host is almost always the mollusc. “Selection of the second intermediate host is less host-specific because cercariae are stimulated to swim by shade and movement” (Eckroad). Echinococcus granulosus belongs to the Cestoidea class. All tapeworms are endoparasites that require at least two hosts. The life cycle of Echinococcus granulosus includes dogs and other canids as definitive...