. Amphioxus and the ancestry of the vertebrates [microform]. Vertebrates; Chordata; Fishes; Ascidiacea; Vertébrés; Cordés; Poissons; Ascidiacés. PA' EORAL LOHE. 271. The very interesting observation has recently been made by MacBride, that the larva of Astcrina gibbosa actually undergoes temporary fixation at the beginning of the metamorphosis, the fixation being effected by the prceoral lobe in a manner strikingly similar to that of the larva^ of Antcdon and of Ciona. In the larva of Antedon the adhering disc, by which the larva eventually fixes itself to some foreign surface, is placed near
. Amphioxus and the ancestry of the vertebrates [microform]. Vertebrates; Chordata; Fishes; Ascidiacea; Vertébrés; Cordés; Poissons; Ascidiacés. PA' EORAL LOHE. 271. The very interesting observation has recently been made by MacBride, that the larva of Astcrina gibbosa actually undergoes temporary fixation at the beginning of the metamorphosis, the fixation being effected by the prceoral lobe in a manner strikingly similar to that of the larva^ of Antcdon and of Ciona. In the larva of Antedon the adhering disc, by which the larva eventually fixes itself to some foreign surface, is placed near the front end of the prcxoral lobe immediately below the apical plate. The central nervous sys- tem of the adult Echinoderm arises in entire indepen- dence of the actual or sup- pressed apical nervous sys- tem Ot the larva, and not at viewed as an opaque ..bject tl»e left all from the ectoderm of the '''*^- *-^^""'' li'dwic) Traioral lobe. prneoral lobe. We have thus seen how within the limits of a single group (viz. the Echinoderms) the pra^oral lobe can become completely emancipated from the central nervous system ; and we have further recognised the fact that whether the cavity of the prai^oral lobe is a derivative of the primary or secondary body-cavity, whether it contains loose mesen- chyme or is lined by an endothelium, the morphological value of the praeoral lobe itself remains the same. THE LORE OF THE PROTOCIIORDATES. It is probable that the misunderstandings and disagree- ments which are of such frequent occurrence among mor- phologists with regard to the comparison of the types of central nervous system presented respectively by the 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 not perfectly resemble the original Willey, Arthur, 1867-1942. New York; London : Mcmillan
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectfishes, bookyear1894
