xvi THE HISTORY OF ZOOLOGY (i4L 



About the middle of the century the vertebral theory, freed 

 from the most obvious absurdities of Oken, was resuscitated and 

 developed by Sir Richard Owen (1803-93) in his Report on 

 the Archetype and Homologies of the Vertebrate Skeleton, published 

 in 1846. He also founded his generalisations on the structure of 

 the adult or late embryonic skeleton in the higher groups, 

 neglecting the unsegmented crania of Cyclostomes and Elas- 

 mobranchs, and of the higher Vertebrate embryo. In his view, 

 the limb-girdles are modified ribs, the shoulder girdle belonging 

 to the " occipital vertebra," while the limbs themselves are 

 " diverging appendages," or uncinates. 



Owen's chief services to Zoology were, however, his numerous 

 and brilliant anatomical researches, such as those on Nautilus, 

 on Apteryx, and on the structure and homologies of the teeth in 

 the entire vertebrate series ; and his palaeontological investigations, 

 especially those on Archa?opteryx,on the fossil Mammals of Australia, 

 and on the Dinornithidae, and other flightless Birds. His conclusion 

 from the examination of a single fragmentary femur, that there 

 had existed in New Zealand a Bird larger and heavier than the 

 Ostrich a fact then practically unknown forms one of the most 

 famous stories in natural history. His contributions to classification 



/ 



were not happy ; he took the nervous system as the basis of his 

 larger divisions, classifying Mammals, for instance, according to 

 the presence or absence of a corpus callosum, and of convolutions, 

 and placing Man in a separate sub-class as the supposed sole 

 possessor of a posterior cornu and hippocampus minor. He 

 rendered great service to philosophical Zoology by pointing out 

 the distinction between homology and analogy, and by the 

 publication of his great text-book on the Anatomy and Physiology 

 of Vertebrates. 



The chief successor of Cuvier in France was Henri Milne- 

 Edwards (1800-18), who enunciated the principle of the 

 division of physiological labour, and modified the classification 

 of Cuvier in several particulars. He separated Tunicates from 

 Mollusca proper, and united them with Polyzoa under the name 

 of Molluscoida, and he divided Vertebrates into Allantoidea and 

 Anallantoidca , according to the presence or absence of an allantois ; 

 in so doing he took the important step of separating Amphibia 

 from Reptiles, a step in which De Blainville had been his only 

 precursor. His learned Legons de I' Anatomic et de la Physiologie 

 compare'e is a storehouse of information on the structure and 

 functions of animals. 



It was not until about the middle of the century that further 

 increase in the knowledge of the lower animals resulted in the 

 gradual dismemberment of Cuvier's unnatural Branch Radiata. 

 Frey and Leuckart established the group Ccelenterata, and 

 placed Echinoderms apart ; Wiegmann removed Rotifera from 



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