. Elementary text-book of zoology. Zoology. 74 MOLLUSCOIDEA. ing to Fr. Miiller there is in Serialaria a so-called colonial nervous system which connects the individual zooids of one colony and enables them to co-ordinate their activities. Claparede * describes the same for Vesicularia, also for Scmpocellaria scruposa and Eugula (avicu- laria). Special organs of sense have not been recognised. Many forms of Bryozoa present examples of a well-marked poly- morphism. In Serialaria and its allies the joints of the stalk represent a special form of individual ; they have a considerable size and a s
. Elementary text-book of zoology. Zoology. 74 MOLLUSCOIDEA. ing to Fr. Miiller there is in Serialaria a so-called colonial nervous system which connects the individual zooids of one colony and enables them to co-ordinate their activities. Claparede * describes the same for Vesicularia, also for Scmpocellaria scruposa and Eugula (avicu- laria). Special organs of sense have not been recognised. Many forms of Bryozoa present examples of a well-marked poly- morphism. In Serialaria and its allies the joints of the stalk represent a special form of individual ; they have a considerable size and a simplified organization, and serve as the ramified sub- stratum on which the nutritive individuals are placed. In addition, there are here and there joints of the roots which, under the form of tendril- and stolon-like processes, serve to attach the colony. The peculiar appendages known as avicularia and vibra- cula, which are modified individuals and seem to have the function of food-procuring organs, are found in many marine Bryozoa. The avicularia (fig. 547, Av) resemble birds' heads and consist of two-armed pincers, which are attached to the colony near the openings of the cells and occasionally snap. They may seize small organisms, , worms, and hold them till they are dead ; the de- composing organic remains are swept into the mouth by the currents caused by the cilia of the tentacles. The vibracula have a similar arrangement, but present in place (after Busk). Te, Tentacular of t}ie snapping beak a long and extremely crown ; R, retractor muscle ; D, alimentary canal ; F, funi- moveable flagelliforni filament (fig. 548). Knal]y there are the Ovicell8 (ooecia), each of which is filled with an egg; they have the form of helmet or dome-shaped appendages and are sessile on the zooecium (fig. 547 Ovz). The reproduction is partly sexual and partly asexual ; in the latter case it may be effected by the so-called statoblasts or by budding. The male and female sexual organs are
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
