310 THE MENTAL CAPACITIES AND 



to be traced among animals now extant, or even when these 

 are intercalated with the remains of the very small frac- 

 tion of extinct forms which have as yet been discovered in 

 the shape of fossil relics, so nothing like a mental serial 

 progression is to be looked for. Whatever the grade of 

 organization of an animal may be, we have, in estimating 

 the nature of its mental processes and powers, to look 

 much to its present sensorial organization and endow- 

 ments. It is true, however, that the experiences of 

 ancestral forms will have had much to do with the basis 

 and background of the creature's Mental Processes, both 

 in special and in general directions. 



If the Mole and its ancestors, owing to their usual con- 

 ditions of life, have had little need of eyes, and these have 

 consequently, in the course of generations, undergone a 

 process of atrophy from disuse, the basis of the mental 

 processes of these particular animals must have been 

 thereby proportionately altered. Sight impressions being 

 cut off, other Sensorial Endowments would have gradually 

 risen in importance for the daily conduct of their life. 

 The sum total of the neural impressions and responses 

 of such animals would, therefore, come to be very different 

 from those of their near ally, the keen-visioned Rat. How 

 different, again, must be the web of sensorial impressions 

 constituting the basis of the mental life of the Stag, into 

 which Scents enter so largely, when compared with that 

 of the Whale, the Porpoise, or the Dolphin, in whom 

 impressions of this order seem to be almost or wholly 

 wanting. 



While there may, therefore, be a general onward pro- 

 gress in the complexity of mental phenomena in different 

 groups of animals, regarded as groups, this general ad- 

 vance may be strangely chequered and interrupted, if we 

 look at its manifestations in individual forms, owing to 



