. An introduction to zoology : for the use of high schools . 26, Like the Brachiopoda, the Polyzoa are bilateral animals,sedentaiy in their adult condition ; they possess a circlet of tenta-cles about the mouth, and are protected by a shell secreted bythe skin, but in other i-espects no resemblance is to be detectedbetween them, except during developmental stages. The factthat the Polyzoa almost invariably form colonies by budding atonce sepai-ates them from the forms heretofore studied; it is tothis peculiarity that the class owes its name. With the exception of Cristatella (Fig, 167), the co
. An introduction to zoology : for the use of high schools . 26, Like the Brachiopoda, the Polyzoa are bilateral animals,sedentaiy in their adult condition ; they possess a circlet of tenta-cles about the mouth, and are protected by a shell secreted bythe skin, but in other i-espects no resemblance is to be detectedbetween them, except during developmental stages. The factthat the Polyzoa almost invariably form colonies by budding atonce sepai-ates them from the forms heretofore studied; it is tothis peculiarity that the class owes its name. With the exception of Cristatella (Fig, 167), the colonies are permanently sedentary, beingattached by an extensive orlimited surface. Accordingto the relative position of thebuds they may be, in thestem of pond-weed. former case, massive, encrust- ing or straggling, in the latter, foliaceous or arborescent (Fig,168). The moss-like form of the colonies has gained the classthe alternative name of Bryozoa. Each individual in the colonysecretes a cell into which the head with the crown of. Fig, 167—Colony of Cristatella, attached to 240 HIGH SCHOOL ZOOLOGY^ tentacles may be withdrawn for protection, and these cellstogether with connecting: tubes constitute the may be of very different character in different foims, beingsometimes gelatinous, but oftener horny or calcareous. Thecolonies may reach a considerable size, but the individualsi-arely exceed one or two lines in length. Most of the Polyzoa fall into two orders, which are nearlyco-extensive with the Fresh-water and Marine forms respec-
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1889
