INTRODUCTION. 21 



encc. Nature, as a celebrated physiologist* has defined it, 

 and as the word was interpreted by the Greeks and Romans, is 

 " that which is ever growing and ever unfolding itself in new 

 forms." 



The series of organic types becomes extended or perfected, 

 in proportion as hitherto unknown regions are laid open to 

 our view by the labours and researches of travellers and 

 observers ; as living organisms are compared with those 

 which have disappeared in the great revolutions of our planet; 

 and as microscopes are made more perfect and are more 

 extensively and efficiently employed. In the midst of this 

 immense variety, and this periodic transformation of animal 

 and vegetable productions, we see incessantly revealed the 

 primordial mystery of all organic development, that same 

 great problem of metamorphosis which Gothe has treated 

 with more than common sagacity, and to the solution of 

 which man is urged by his desire of reducing vital forms to 

 the smallest number of fundamental types. As men contem- 

 plate the riches of nature, and see the mass of observations 

 incessantly increasing before them, they become impressed 

 with the intimate conviction that the surface and the interior 

 of the earth, the depths of the ocean, and the regions of air 

 Mill still, when thousands and thousands of years have passed 

 away, open to the scientific observer untrodden paths of dis- 

 covery. The regret of Alexander cannot be applied to the 

 progress of observation and intelligence.! General consi- 

 derations, whether they treat of the agglomeration of matter in 

 the heavenly bodies, or of the geographical distribution of 

 terrestrial organisms, are not only in themselves more attrac- 

 tive than special studies, but they also afford superior advan- 

 tages to those who are unable to devote much time to occupa- 

 tions of this nature. The different branches of the study of 

 natural history arc only accessible in certain positions of 

 social life, and do not at every season and in every climate 

 present like enjoyments. Thus, in the dreary regions of the 

 north, man is deprived for a long period of "the year of the 

 spectacle presented by the activity of the productive forces of 

 organic nature; and if the mind be directed to one sole class 



* Carus, Von den Urtheilen des Knochen nnd Schalen Gcriistes, 

 1828, 6. 



f Plut., in Vita Alex. Mar/ni, cap. 7. 



