INTRODUCTION. 9 
we should be all agreed that in the case of these 
animals the life is so very thin-spun that any 
suggestion of abhorrence is on the face of it 
absurd.* 
* The relation of consciousness to the elaboration of nerve- 
centres throughout the animal kingdom is more fully considered 
in my work on “ Mental Evolution in Animals” (Kegan Paul, 
Trench & Co. : 1883). 
