A combination of factors is likely causing the decline of blue spruce trees throughout Michigan. Posted on March 7, 2011 by Dennis Fulbright, Michigan State University Extension, Department of Plant Pathology, and Jill OâDonnell, Michigan State University Extension.
Flatworms lack a respiratory or circulatory system; these functions take place by absorption through the body wall. Nonparasitic forms have a simple, incomplete gut; even this is lacking in many parasitic species. Movement in some flatworms is controlled by longitudinal, circular, and oblique layers of muscle.
FlatwormsPlatyhelminthes. Structure. Flatworms are flat, soft bodied, ribbon shaped unsegmented, contain no body cavity, but they do have digestive cavity. They are bilateral symmetrical, while having only one opening. Flat worms have layers of tissues that surround their central gut. They are part of the acoelomates, and are considered hermaphroditic.