CLASSIFICATION OF THE POLYZOA.
I.
Synopsis of the Subclasses, Orders, and Suborders.
Class POLYZOA.
Small cœlomate animals, each individual of which consists of a polyp-like organism or polypide enclosed in a "house" or zoœcium composed partly of living tissues. The mouth is surrounded by a circle of ciliated tentacles that can be retracted within the zoœcium; the alimentary canal, which is suspended in the zoœcium, is Y-shaped and consists of three parts, the œsophagus, the stomach, and the intestine.
Subclass ENTOPROCTA.
The anus as well as the mouth is enclosed in the circle of tentacles and the zoœcium is not very distinctly separated from the polypide. Some forms are solitary or form temporary colonies by budding.
Most Entoprocta are marine, but a freshwater genus (Urnatella) occurs in N. America, while the Indian genus Loxosomatoides (fig. 34, p. 176) is only known from brackish water.
Subclass ECTOPROCTA.
The anus is outside the circle of tentacles and the zoœcium can always be distinguished from the polypide. All species form by budding permanent communities the individuals in which remain connected together by living tissue.