210 ON THE ANIMAL KINGDOM. 



the individual, it may be said of the f ertehrata, at least, 

 that there are as many sorts of inteUigence displayed as 

 there are individual beings, whilst of insects there are pro- 

 bably as many degrees of instinct as there are species. 



It is also obvious that we cannot, without confusion, 

 compare with each other in degree the different sorts of 

 intelligence displayed by animals whose general structure 

 is not only different, but also their nervous system, on the 

 disposition of which their inteUigence in so great a mea- 

 sure depends. Where indeed the intelligence is of the 

 same sort, we may estimate its degree; but this can only be 

 where all the beings under consideration are referable to 

 the same type of form ; and, above all, where their nerv- 

 ous matter has been dispersed on the same general plan. 

 But as this is a subject I purpose hereafter more fully to 

 discuss, I shall conclude this chapter with observing, that 

 it must afford pleasure to those who have a taste for the 

 analogies of nature, to perceive that no where are they more 

 visible than between the animal and vegetable kingdoms. 

 The difference which separates these appears to depend, 

 as we have already shown, on the presence of a nervous 

 system in animals. Yet it is worthy of attention, that those 

 vegetables which are generally supposed to make the near- 

 est approach to the other kingdom possess a degree of irrita- 

 bihty, the cause of which has long excited the curiosity of 

 philosophers, but as constantly baffled their efibrts to detect 

 it. The chemical analysis also of the lower tribes of plants 

 indicates the presence of azote ; and though it has been as- 

 serted that the irritability of the genus Lirickia, or Nostochs, 

 is entirely owing to the elasticity of the plant, and by no 

 means to any nervous action ; yet allowing this to be the 

 case, we can only admire the beautiftd regularity of nature, 



