SOME MOOT POINTS IN NATURAL 

 HISTORY. 



ONE of the most remarkable features included in the study 

 of living beings, is the marvellous plasticity, if one may so 

 term it, of form and function which is everywhere exhibited 

 in the domain of living nature. The variety of form pre- 

 sented by the animal and plant worlds is a matter of common- 

 place remark, and the fertility of contrivance wherewith the 

 aims and ends of life of every grade are subserved and 

 carried out, forms a subject of equally plain and obvious 

 kind. So diverse, indeed, are the aspects of natural-science 

 study, as distinguished from those presented by the exact or 

 mathematical sciences, that the methods of the latter are 

 almost wholly inapplicable to the investigation of living 

 beings. Nowhere is the plasticity of living nature better 

 seen than when the naturalist attempts to frame an 

 exact definition of a group of animals or plants. Let his 

 terms be ever so plain, exact, and apparently applicable, it 

 will invariably be found that one or more of the beings 

 included in the proposed group will exhibit characters which 

 to a greater or less extent fall without the bounds of the 

 definition. Hence arise the difficulties which beset the 

 merest tyro in zoology or botany who attempts to understand 

 the various systems of classification which from time to time 

 have represented the desire of scientists to place their be- 

 longings in satisfactory order and arrangement. And hence 

 also have originated the numerous subordinate groups and 



