The structure of animal life : six lectures delivered at the Brooklyn Academy of Music in January and February, 1862 / by Louis Agassiz.

  • Louis Agassiz
Date:
1866
Catalogue details

Licence: Public Domain Mark

Credit: The structure of animal life : six lectures delivered at the Brooklyn Academy of Music in January and February, 1862 / by Louis Agassiz. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    widely from one another. One is essentially aquatic; the animals are hatched from eggs, and in the form of tadpoles live like fish in the water, and undergo a succession of very striking changes. They are not born in the form of the adult animal; every Frog or Toad is at first a Tadpole, which has gills like a Fish instead of lungs. Gradually, however, it loses its tail, puts forth legs, develops lungs instead of gills, and assumes the character- istics of an air-breathing animal. The other class, embracing Snakes, Lizards, (not Salamanders, which are erroneously called Lizards, but which belong to the Frog tribe,) the Crocodile, the Alli- gator, the Tortoise, all have a very different mode of development. Their eggs are like Birds' eggs, and their young when hatched have the form of the adult, with no further change except in growth. They breathe through lungs at birth, like the adult Eeptile. You see at once, that there is reason for placing these fish-like Reptiles-lowest in the scale, in consequence of their resemblance to Fishes, and the air-breathing Reptiles highest, because in that respect they resemble Birds and Mammals. This is then the order of Reptiles : Salamanders (commonly called, in the Northern States, Water- dogs) lowest, then terrestrial Salamanders, then Frogs and Toads; and from these we pass at once to the scaly Reptiles. If we attempt to establish an order among the scaly Reptiles, we find that Serpents, on account of the absence of locomotive organs, and on many other accounts, (I have not time to go into the anatomical details,) rank the
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