. Cassell's natural history. Animals; Animal behavior. AXATOMY OF THE opening, and is therefore vnthin the disc or stage from which those brcatliing organs originate. Botli groups liaving the breathing organs or tentacles in a continuous series, are comprised in the Holo- hranchiata.* A third and somewliat abnormal form, Rhabdopleura (Fig. 18, a), having a divided or winged base for the tentaclesâwhich from their mobility and position pi-esent a close resemblance to the brachial organs of the Brachiopodâat present constitutes the section Pterobranchiata. The Moss-animals, whether in
. Cassell's natural history. Animals; Animal behavior. AXATOMY OF THE opening, and is therefore vnthin the disc or stage from which those brcatliing organs originate. Botli groups liaving the breathing organs or tentacles in a continuous series, are comprised in the Holo- hranchiata.* A third and somewliat abnormal form, Rhabdopleura (Fig. 18, a), having a divided or winged base for the tentaclesâwhich from their mobility and position pi-esent a close resemblance to the brachial organs of the Brachiopodâat present constitutes the section Pterobranchiata. The Moss-animals, whether in the form of a minute .shrub sprung from a creeping root-thread (Fig. 16), or occuiTing in bi-anched and riband-like encrusting masses, almost invariably consist of a colony of individuals protected by a common external skeleton or coenoecium,t which forms a defensive covering like the shell of a mollusc, differing, however, from that structure, inasmuch as once formed it seems to have no further connection with the animal that originally secreted it, surviving its death, and increasing independently. The assemblage of cells forming the composed of no eality of a truly. Fig. 18.âA, wixc CKESCENTIC, C, CIRCULAR T\TK OV GILL TENTACLES, ENLARGED, (After Hancoclc and Ray Lankester ) II, Mouth ; a,Ann«, o Nci \e ganglion . or foot : /, Divided or Winged colony or polyzoariui cellular nature, and present in the higher forms of the class. (F. A. Smitt.) First comes the tnie ani- mal cell, the zooe- cium, which lodges a perfect Moss- animal. Two other kinds, devoid of inhabitants, have become metamor- phosed into purely defensive organs; â while some, the ovi- cells, are restricted to reproductive pur- poses. The stem-cells are simply elongated animal chambers; and lastly, the radical-cells, or root- fibres, which, sometimes hooked, act like little grapnels, mooring the colony to the soft organisms to which it is attached, or, directed upwards, terminate in free, tendr
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