http://en.wikipedia.org/wiki/Mouth
Some animal phyla, including vertebrates, have a complete digestive system, with a mouth at one end and ananus at the other. Which end forms first in ontogeny is a criterion used to classify animals into protostome and deuterostome.
Some animal phyla, including vertebrates, have a complete digestive system, with a mouth at one end and ananus at the other. Which end forms first in ontogeny is a criterion used to classify animals into protostome and deuterostome.
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