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Especially in the lowest of all the vertebrates, the lancelet or Amphioxus, we have the oldest stem-forms completely preserved in the embryonic development. We also find important evidence in the fishes, which stand between the lower and higher vertebrates, and throw further light on the course of evolution in certain periods.
As a fact, the highest summit of the vertebrate organisation which man represents is in every respect so far above the lowest stage, at which the lancelet remains, that one would at first scarcely believe it possible to class both animals in the same division of the animal kingdom. Nevertheless, this classification is indisputably just.
But they are far below the true fishes, and form a very interesting connecting-group between them and the lancelet. One can see how closely they approach the latter by comparing a young lamprey with the Amphioxus. The chorda is of the same simple character in both; also the medullary tube, that lies above the chorda, and the alimentary canal below it.
Gonepteryx Rhamni, sexual difference of colour in. Goodsir, Prof., on the affinity of the lancelet to the ascidians. Goosander, young of. Goose, Antarctic, colours of the. Goose, Canada, pairing with a Bernicle gander. Goose, Chinese, knob on the beak of the. Goose, Egyptian. Goose, Sebastopol, plumage of. Goose, Snow-, whiteness of the. Goose, Spur-winged.
Arts practised by savages. Ascension, coloured incrustation on the rocks of. Ascidia, affinity of the lancelet to; tad-pole like larvae of. Ascidians, bright colours of some. Asinus, Asiatic and African species of. Asinus taeniopus. Ass, colour-variations of the. Ateles, effects of brandy on an; absence of the thumb in. Ateles beelzebuth, ears of.
Here he adopts the investigations of A. Kowalewsky, and the deductions of Häckel founded upon them, concerning the larva of the ascidiæ, a genus of marine mollusca of the order tunicata, and sees in a cord, to be found in this larva, most decided relationship to the spine of the lancelet fish or amphioxus, the lowest of all the vertebrates, it being yet doubtful whether it belongs at all to the vertebrates.
Lamarck, on the origin of man. Lamellibranchiata. Lamellicorn beetles, horn-like processes from the head and thorax of; influence of sexual selection on. Lamellicornia, stridulation of. Lamont, Mr., on the tusks of the walrus; on the use of its tusks by the walrus; on the bladder-nose seal. Lampornis porphyrurus, colours of the female. Lampyridae, distasteful to mammals. Lancelet.
Within the highest division of the animal kingdom, namely, the Vertebrata, we can start from an eye so simple, that it consists, as in the lancelet, of a little sack of transparent skin, furnished with a nerve and lined with pigment, but destitute of any other apparatus. In fishes and reptiles, as Owen has remarked, "The range of gradation of dioptric structures is very great."
With fishes, members of the shark family would not tend to supplant the lancelet; for the lancelet, as I hear from Fritz Muller, has as sole companion and competitor on the barren sandy shore of South Brazil, an anomalous annelid.
The fossil referred to is an ancient fish-like worm, or worm-like fish, to which the name of Entomicthys amphisoma has been provisionally given. It is still more remarkable than the amphioxus or lancelet, which has been long known.
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