INTRODUCTION. 41 



forces — ill that inextricable net- work of organisms by turns 

 developed and destroyed — each step that we make in the 

 more intimate knowledge of nature leads us to the entrance 

 of new labyrinths ; but the excitement produced by a presenti- 

 ment of discovery, the vague intuition of the mysteries to be 

 unfolded, and the multiplicity of the paths before us, all tend 

 to stimulate the exercise of thought in every stage of knowl- 

 edge. The discovery of each separate law of nature leads to 

 the establishment of some other more general law, or at least 

 indicates to the intelligent observer its existence. 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 labors and researches of travelers and observers ; 

 as living organisms are compared with those which have dis- 

 appeared in the great revolutions of our planet ; and as micro- 

 scopes 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 pro- 

 ductions, we see incessantly revealed the primordial mystery 

 of all organic development, that same great problem of meta- 

 Tnorpliosis which Gothe has treated with more than common 

 sagacity, and to the solution of which man is urged by his 

 desire of reducuiEr vital forms to the smallest number of fun- 

 damental types. As men contemplate the riches of nature, 

 and see the mass of observations incessantly increasing be- 

 fore them, they become impressed with the intimate convic- 

 tion that the surface and the interior of the earth, the depths 

 of the ocean, and the regions of air will still, when thousands 

 and thousands of years have passed away, open to the scien- 

 tific observer untrodden paths of discovery. The regret of 

 Alexander can not be appUed to the progress of observation 

 and intelligence.! General considerations, 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 attractive than special studies, but 

 they also afford superior advantages to those who are unable 

 to devote much time to occupations of this nature. The dif- 

 ferent branches of the study of natural history are only accessi- 

 ble in certain positions of social life, and do not, at every sea- 



* Cams, Von den Urtheilen des Knochen und Schalen Gerustes, 18"2^ 

 $ 6 + Plut., in Vita Alex. Magni, cap. 7 



