WHAT ARE SPECIES f 4 i 3 



It is mainly to the influence of Cuvier's authority that we owe the 

 general acceptance of the views respecting the physiological charac- 

 ter of species, which up till within the last few years have been almost 

 universally prevalent. 



In the introduction to the " Regno Animal " (1816), Cuvier writes: 



''There is no proof that all the differences which now distinguish organized 

 beings are such as may have been produced by circumstances. All that has 

 been advanced upon this subject is hypothetical ; experience seems to show, on 

 the contrary, that, in the actual state of things, varieties are confined within 

 rather narrow limits, and, so far as we can retrace antiquity, we perceive that 

 these limits were the same as at present. 



" We are thus obliged to admit of certain forms, which since the origin of 

 things have been perpetuated, without exceeding these limits ; and all the be- 

 ings appertaining to one of these forms constitutes what is termed a species. 

 Varieties are accidental subdivisions of species. 



" Generation being the only means of ascertaining the limits to which varie- 

 ties may extend, species should be defined, the reunion of individuals descended 

 from one another, or from common parents, or from such as resemble them as 

 closely as they resemble each other ; but, although this definition is vigorous, it 

 will be seen that its application to particular individuals may be very different 

 when the necessary experiments have been made." 



It need hardly be said, however, that in practice Cuvier founded 

 his species upon purely and exclusively morphological characters, just 

 as his predecessors and successors have done. The combination of 

 Cuvier's views on thenxity of species with the discovery of the suc- 

 cession of life on the globe, which was so largely the result of his 

 labors, led his successors into curious difficulties. Developing the 

 fundamental idea of the " Discours sur les Revolutions de la Surface 

 du Globe," naturalists were forced to conclude not only that existing 

 species are the result of creation, but that the creative act by which 

 they were brought into being was only the last repetition of a series 

 of such acts by which the often depopulated world has been as fre- 

 quently sepeopled, and thus orthodox belief respecting the existing 

 flora and fauna led to a terribly heterodox cosmogony. 



The contemporary and countryman of Cuvier, Lamarck, must be 

 regarded as the chief founder of the reaction against the doctrines 

 which Cuvier advocated a reaction which, overpowered and disre- 

 garded for many years, has acquired such force since and through the 

 publication of the " Origin of Species," that it has almost swept op- 

 position away. Lamarck's vast acquaintance with the details of in- 

 vertebrate zoology rendered him familiar with the great variability 

 of many species, and led him to see that variation is in some way 

 related to change of conditions; the frequent occurrence of transi- 

 tional forms between apparently distinct species, when large suites of 

 specimens (especially when they are obtained from different parts of 

 a wide geographical area) are examined, tended to bring into strong 



