. Text-book of zoology for junior students. Zoology. DIVISIOXS OF THE HYDEOZOA. 61 Order II. Gorynida. In the second order of the Hydroid Zoophytes, known as the Corynida or Tuhularida, we have a number of organisms which in their essential structure are closely relate<.l to the Hydra, but which differ considerably in the nature of the reproductive pro- cess. All of them are marine, with the single exception of the genus Cordylophora, which inhabits fresh water. Some of the members of the order are simple, consisting of no moie than a single poly]iite. In these cases there is an exceedingly
. Text-book of zoology for junior students. Zoology. DIVISIOXS OF THE HYDEOZOA. 61 Order II. Gorynida. In the second order of the Hydroid Zoophytes, known as the Corynida or Tuhularida, we have a number of organisms which in their essential structure are closely relate<.l to the Hydra, but which differ considerably in the nature of the reproductive pro- cess. All of them are marine, with the single exception of the genus Cordylophora, which inhabits fresh water. Some of the members of the order are simple, consisting of no moie than a single poly]iite. In these cases there is an exceedingly close ap- proach to the structure of the com- mon Hydra, but the jjolypite is permanently fixed without the power of voluntarily changing its place, whilst the I'eproductive pro- cess is considerably diff'erent. In the majority of the Corynida, how- ever, the hydrosoma is compound, consisting of a greater or less num- ber of separate polypites or zooids, all connected with one another by a common flesh or coenosarc, and all forming parts of a plant-like rooted colony. In scjnie of the Corynida the polypites are naked, but in most cases the crenosarc is protected by a horny-locjking chit- inous ^ envelope or " polypary," as in I'uhularia indivisa (fig. 31). In no case, however, is this horny covering so prolonged as to form little cups in which each jiolypite is contained. It always stops short at the bases of the polypites, and in this way the Corynida can always be distinguished from their near allies, the Sea-firs {Sertularida). Good examples of the Corynida are the common Pipe - corallines (Tiibidaria), in which the cwnosarc is enclosed in a homy tubular polypary (fig. 31), each tube containing a single polypite. Other ' Chitine is a suTistance wliicli is nearly allieil to horn, luit is distinguished from it by the fact that it is not soliOJe in caustic 31.—Fragment of Tvlndaria indirim, natural Please note that these images are extracted from sc
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1885
