Endoskeleton three phyla and one subclass of animals, endoskeletons of various complexity are found: Chordata, Echinodermata, Porifera, and Coleoidea. An endoskeleton may function purely for support (as in the case of sponges), but often serves as an attachment site for muscle and a mechanism for transmitting muscular forces. A true endoskeleton is derived from mesodermal tissue. Such a skeleton is present in echinoderms and chordates. The poriferan 'skeleton' consists of microscopic calcareous or siliceous spicules or a spongin network. The Coleoidae do not have a true endoskeleton in the evolutionary sense; there, a mollusk exoskeleton evolved into several sorts of internal
Anelida and Arcite Anelida and Arcite Anelida and Arcite is a 357-line English poem by Geoffrey Chaucer. It tells the story of Anelida, queen of Armenia and her wooing by false Arcite from Thebes, Greece. Although relatively short, it is a poem with a complex structure, with an invocation and then the main story. The story is made up of an introduction and a complaint by Anelida which is in turn made up of a proem, a strophe, antistrophe and a conclusion. After the complaint there are a few lines which continue the story, but these may have been added by a later