228 PHILOSOPHY OF ZOOLOGY. 



number of concentric circles of the vertebrae and scales of 

 fishes, have been regarded, in the absence of experience, as 

 indicating the age of the animal to which they belong. 

 Even the age of the Earth, apparently, in the opinion of 

 some geologists, may be determined by regarding its strata, 

 as analogous to the layers of growth in a tree. 



An anatomist of eminence observed, that the cells of a 

 piece of bee-comb which he examined were double *, The 

 acute author of the article, " Vegetable Anatomy," in the 

 Supplement to the Encyclopaedia Britannica yields to the 

 opinion, that the cells of plants are double, influenced by 

 this observation of the condition of the cells of bees. 



Since the windpipe of birds is employed to convey air to 

 and from the lungs, vegetable physiologists have ever 

 been inclined to consider the spiral vessels of plants, which 

 have a remote resemblance thereto, as likewise air-vessels,- 

 and much vain reasoning and idle conjecture, have in con- 

 sequence been displayed on the subject. 



As the materials of the crust of the earth are lighter than 

 the mean density of the earth, many geologists conclude, 

 that the weighty materials of the centre must be metallic, 

 without attending to the condition which must be produced 

 by the force of gravitation, or the analogous arrangement 

 of the atmosphere. Whoever risked the conjecture, that 

 the lower and denser parts of the atmosphere, were of a 

 more metallic nature than the higher and lighter parts ? 



On what foundation does the belief rest, that the other 

 planets are inhabited, but on that of analogy ; yet the cir- 

 cumstances of the other planets are all different with re- 

 gard to the force of gravity, motion, temperature, and 

 light. Their inhabitants, therefore, if such exist, must be 

 unlike us in physical constitution at least, neither bone of 

 our bone, nor flesh of our flesh. 



Mem. Wern. Soc. ii. p. 59 



