CHAP. XIII.] LOWER ANIMALS. 201 



nervous systems, and where, therefore, conscious guidance 

 may have been ahsent even at the time when the struc- 

 tural correlatives of the movements were originally or- 

 ganized. 



Yet, in spite of the acknowledged source of uncertainty 

 in regard to this criterion, it must be confessed that we are, 

 to a great extent (for want of any better guide), driven to 

 look to this very quality of 'fitness,' in reference to the 

 nature of actions and the impressions which instigate 

 them, as our chief though very uncertain means of form- 

 ing an opinion concerning the probable presence, amount, 

 or kind of Conscious Intelligence in animals generally. 

 We have to look especially to the range, complexity, and 

 degree of adaptation of the movements to varying cir- 

 cumstances and to unfamiliar conditions ; and we are 

 accustomed, in addition, to look to the degree of develop- 

 ment of the Nervous System in the animals under 

 observation. 



(2.) The same kind of difficulty presents itself in an- 

 other form, with regard to such animals as Insects, Cepha- 

 lopods, Fishes, Eeptiles, and Birds. These organisms are 

 so high in the scale of organization, as to leave almost no 

 room for doubt that some of their nerve actions are attended 

 by Conscious States, but it is impossible for us definitely to 

 decide, which are, and which are not, so endowed. 



Two principal difficulties stare us in the face. First 

 there is the necessity for the caution on which we have last 

 dwelt, in respect to drawing conclusions from the degree 

 of ' fitness' noticeable in the nature of the response ; and 

 second, there is the further difficulty that our own experience 

 can only be taken as a very uncertain guide. Impressions 

 of certain kinds, which, in ourselves, are no longer attended 

 by Conscious States, may, nevertheless, be commonly accom- 



