A+E Networks. In Tokyo, Commodore Matthew Calbraith Perry, representing the U.S. government, signs the Treaty of Kanagawa with the Japanese government, opening the ports of Shimoda and Hakodate to American trade and permitting the establishment of a U.S. consulate in Japan.
Platyhelminthes are mostly worm like creatures that are dorsoventrally flattened, meaning they look like a ribbon, this is why they are called names such as Tapeworm, Flatworm, Fluke and Planarian. The Platyhelminthes are a successful phylum with around 25,000 known species divided into four classes. Most Platyhelminthes are parasites on other animals, only the Turbellarians are mostly non-parasitic. A few species are commensalists living in harmony, or mutual benefit with another, normally larger organism. Most species feed on animal material either as parasites or as scavengers, a very few species feed on algae.
These animals possess three living cell layers (i.e.: ectoderm, mesoderm, and endoderm) which makes them triploblastic. The platyhelminths, or flatworms are an economically important group because they include the parasitic tapeworms and flukes, which affect both humans and the livestock we depend on. These acoelomates are advanced over other radiate animals in several ways: 1. Their bilateral symmetry adapts them for direct movement. 2.