. The chordates. Chordata. :;i: Comparative Anatomy—Its History, Aim, and Method. Fig. 275 {Left). Erasmus Darwin (1731-1802). (Courtesy, Locy: "Biology and Its Makers," New York, Henry Holt & Co., Inc.) Fig. 276 (Right). Geoffroy Saint-Hilaire (1772-1844). (Courtesy, Locy: "Biology and Its Makers," New York, Henry Holt & Co., Inc.) Geoffroy Saint-Hilaire was preeminently an investigator of the comparative anatomy of vertebrates. His particular achievement was his demonstration of the "unity of plan" in all vertebrate animals. He gave much attention to the
. The chordates. Chordata. :;i: Comparative Anatomy—Its History, Aim, and Method. Fig. 275 {Left). Erasmus Darwin (1731-1802). (Courtesy, Locy: "Biology and Its Makers," New York, Henry Holt & Co., Inc.) Fig. 276 (Right). Geoffroy Saint-Hilaire (1772-1844). (Courtesy, Locy: "Biology and Its Makers," New York, Henry Holt & Co., Inc.) Geoffroy Saint-Hilaire was preeminently an investigator of the comparative anatomy of vertebrates. His particular achievement was his demonstration of the "unity of plan" in all vertebrate animals. He gave much attention to the correspondence of certain organs of different animals. For example, a foreleg of a quadruped, the wing of a bird, and the human arm correspond anatomically. They are consti- tuted of similar parts similarly related to one another and to the body. In spite of their very unlike form, they correspond and must be regarded as the same or homologous organs. He did not accept Lamarck's causal explanation of evolution, but believed that evolutionary change resulted from direct action of environment on the structures of an or- ganism. Also in contrast to Lamarck, who believed that all evolution- ary change was very gradual, Saint-Hilaire maintained that major changes may occur abruptly ("saltatious"—, evolution by leaps). He went so far as to suggest that the original bird may have hatched from the egg of some reptile. Cuvier's great work as a comparative anatomist covered not merely the vertebrates but the whole animal kingdom. His study of collections of fossil bones found near Paris marked the beginning of the science of Vertebrate Paleontology. But he was decidedly fact-minded and so found himself at odds with some of his philosophic contemporaries. He deplored their speculative habit of thinking and claimed that it led them to absurd vagaries. He seemed content with "special creation" as an explanation of the beginning of things. His controversy with Sa
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