The History of Creation; Or, the Development of the Earth and Its Inhabitants by the Action of Natural Causes

The History of Creation; Or, the Development of the Earth and Its Inhabitants by the Action of Natural Causes : A Popular Exposition of the Doctrine of Evolution in General, and of That of Darwin, Goethe and Lamarck in Particular

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1876 edition. Excerpt: of the body during the embryological development out of the egg, originally begin in the same simple form, which is retained throughout life by the Amphioxus. It is only at a later period that the brain develops by the expansion of the fore end of the spinal marrow, and out of the spinal rod the skull which encloses the brain. As these two important organs do not develop at all in the Amphioxus, we may justly call the class represented by it, Skull-less animals (Acrania), in opposition to all the others, namely, to the animals with skulls (Craniota). The Skull-less animals are generally called tubular-hearted (Leptocardia), because a centralized heart does not as yet exist, and the blood is circulated in the body hy the contractions of the tubular blood-vessels themselves. The Skulled animals, which possess a centralized, thick-walled, bulb-shaped heart, ought then by way of contrast to be called bulbular-hearted animals (Pachycardia). ASCIDIANS RELATED TO VERTEBRATES. 201 Animals with skulls and central hearts evidently developed gradually in the later primordial period out of those without skulls and with tubular hearts. Of this the ontogeny of skulled animals leaves no doubt. But whence are these same skull-less animals derived? It is only very lately that an exceedingly surprising answer has been given to this important question. From Kowalewsky's investigations, published in 18C7, on the individual development of the Amphioxus and the adhering Sea-squirts (Ascidia) belonging to the class of mantled animals (Tunicata), it has been proved that the ontogenies of these two entirely different looking animal-forms agree in the first stage of development in a most remarkable manner. The freely swimming larvae of the Ascidians (Plate...
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Product details

  • Paperback | 112 pages
  • 189 x 246 x 6mm | 213g
  • United States
  • English
  • black & white illustrations
  • 1236959140
  • 9781236959140