Abstract
ZOOLOGICAL CLASSIFICATION.—In a recent paper in Pfliiger's Archiv, M. Hoppe-Seyler wonders at the readiness with which systematic zoology has ranked amphioxus with the vertebrates, from mere one-sided consideration of the presence of a chorda dorsalis, and the position of the nerve-cord above, and the alimentary canal below. A sound system groups species which are similar not merely in morphological respects, but in their whole organisation. Amphioxus has, beyond the chorda, nothing in common with vertebrates; it has no closed vascular system with red blood corpuscles, no liver which forms a gall, no proper brain, and it contains no gelatine-yielding tissue, which occurs in all vertebrates and also in the cephalopoda, but in no other inveitebrata. In their entire highly-developed organism, the cephalopoda, stand nearest to the vertebrata; the amphioxus should have a place further down. M. Hopps-Seyler further points out that comparing the composition of tissues from the lower organised animals upwards, we meet first with mucin yieldiog tissues, then with those yielding chondrin, then, in the cephalopoda tissues yielding glutin; the formation of actual bones does not occur in all vertebrata, and is likewise wanting in cephalopoda. Exactly the same order is seen in the stages of development of an embryo, e.g. of the hen in the egg, and it is difficult to think that the agreement is accidental.
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Biological Notes . Nature 16, 30–31 (1877). https://doi.org/10.1038/016030a0
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DOI: https://doi.org/10.1038/016030a0