180 STUDY OF NATURAL HISTORY. 



enquiries touching the purposes for which an animal 

 has been created, and what influence it possesses in 

 the economy of the universe, we pass the boundaries 

 of simple fact, and are compelled, in most cases, to 

 rely upon theory. True it is, as in the instances 

 just given, we can be at no loss to discover the 

 more general uses of animals : for example, we know 

 that some supply food to others, or hasten the de- 

 composition of decayed matter ; that some promote 

 the fecundation of plants, or check the exuberance 

 of vegetation. These may still be admitted in the 

 list of unquestionable truths, because they are mani- 

 fest to ordinary observers. But when we enquire 

 into more minute particulars, and speculate on the 

 reasons why the flamingo, for instance, has such 

 disproportionately long legs ; what particular pur- 

 poses of nature are fulfilled by the ostrich; or 

 what are the particular uses for which such an 

 apparently anomalous animal as the ornithorynchus, 

 — half quadruped, half bird, — was created; when, 

 in short, we attempt to discover the uses of such 

 animals of which direct evidence cannot be pro- 

 duced ; we enter upon a boundless region of specu- 

 lation and theory, — a region which the student 

 should avoid, and where the more experienced 

 naturalist will do well to proceed with caution. 

 In the mean time, such considerations should not 

 deter us from accumulating facts connected with 

 animal economy, or from recording such inferences 

 as may be plausibly drawn from them ; leaving the 

 validity of these inferences to be confirmed or dis- 

 proved by longer experience. 



(122.) There is a third consideration regarding 



