CEREBRAL HEMISPHERES AND MEMORY 251 



Invertebrates they will probably be found in the 

 supracesophageal ganglion. 



5. The spinal-cord-soul is not the only instance in 

 which biologists have been led astray by their blind 

 acceptance of metaphysical notions. A second and 

 perhaps more general instance is the assumption that 

 consciousness exists in every animal and is present to 

 a certain degree even in the egg. Many authors ob- 

 ject to the idea that a thing like consciousness or the 

 soul should get into the body suddenly at a certain 

 stage of development. What they consider true for 

 the ontogenetic development they also assume for the 

 phylogenetic development, and they are led to believe 

 that each animal possesses consciousness. All these 

 speculations collapse as soon as we free ourselves 

 from the influence of metaphysics, and realise that 

 the term consciousness or soul is applied by meta- 

 physicians to phenomena of associative memory, and 

 that the latter depends upon a physical mechanism 

 which must be just as definite as, for example, the 

 dioptrical apparatus of our eye. I do not think that 

 anybody maintains that every animal must have an 

 apparatus which unites the rays of light emanating 

 from a luminous point to an image point on the sur- 

 face of its body, simply because certain animals have 

 such an apparatus. Moreover, I do not believe that 

 even our biological metaphysicians assume that this 

 dioptrical apparatus exists already in the human egg, 

 and that the latter is already capable of visual space- 

 perception, because it would be too awkward to as- 



