. An introduction to zoology, with directions for practical work (invertebrates). POL YZOA 99 The tentacles are numerous, and are united at their base to form a funnel-like structure at the bottom of which is the mouth. A careful study of such Polyzoans has revealed that within each zooecium is a lining of living cells, and within this a body-cavity (a true coelom) containing a U- shaped alimentary canal, the anus opening close to the mouth of the zooecium (cp. Bugula, Fig. 52). A rudimentary nervous system is present, but no vascular system. In Flustra there are no excretory organs, but these
. An introduction to zoology, with directions for practical work (invertebrates). POL YZOA 99 The tentacles are numerous, and are united at their base to form a funnel-like structure at the bottom of which is the mouth. A careful study of such Polyzoans has revealed that within each zooecium is a lining of living cells, and within this a body-cavity (a true coelom) containing a U- shaped alimentary canal, the anus opening close to the mouth of the zooecium (cp. Bugula, Fig. 52). A rudimentary nervous system is present, but no vascular system. In Flustra there are no excretory organs, but these occur in some Polyzoa. Anothervery PoSa. ^^""il^^ fo™ is Flustrella his- pida, but this only occurs Fig. 52.—The Bird'sHead Coralline (i3»- , ,. J. ., gulaavicularia). Tv/ozooids much mag- as encrustations, frequently ^ (Fiom Parker and Haswell.) OIU UCUS. jj„^ Anus; ai-ic, avicuiaria; emb, an embryo; MembvanipOra is another funic, funiculus; mo, mouth; stom, stomach; genus which makes a »". ovary; .p, spermary. whitish lace-like encrustation on Laminaria. In Bugula avicularia, the common Bird's- Head Coralline, the colony has a tree-like form, and may be several inches high. It forms brownish or purple tufts on rocks or pieces of wood in the sea. Bugula turUnaia has a spiral form (Fig. 53). Fig. 53. —/j «,-/(( a j ^j^- „gjjyg gg^^jj zooecium has attached turbinata, a small . ,. , , , ,., i . i, colony, natural to it a cunous little body, very like a birds size. (From (he head, called an ^' ; The " beak " Srfr '^'"'"'"^ of *^'^ structure is constantly moving, the two parts of it opening and shutting again with a snap. Eejuvena- ^ curious feature in the life-history of these tion. Polyzoa is the way in which at times the central. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherlondo, bookyear1913
