66 Instinct and Intelligence 



at best, as Prof. Huxley remarks, a term em- 

 ployed "when we do not know anything about 

 the -cause of any phenomena." It would be 

 well for science if we could rid ourselves of 

 such phrases, for modern scientific ideas can 

 accept no theory which is not founded upon 

 continuity of phenomena, whether physical or 

 psychical. 



The bodies of jelly-fish and star-fish have 

 neither a head nor tail, neither right nor left 

 side, an arrangement which is sufficient to meet 

 the needs of beings whose food is brought to 

 them floating in the water by which they are 

 surrounded. But when from geological or other 

 changes in their environment animals of this 

 description have been compelled to pass from 

 an aquatic to a terrestrial mode of life, and 

 therefore to search for their food, or for a mate, 

 and to protect themselves from enemies, the 

 various kinds of protoplasm constituting the 

 basic substance of the structures of the " fittest " 

 of these beings must have responded ade- 

 quately to the incidence of the forces acting on 

 them, and thus gradually developed a nervous 



1 Huxley's Essays, p. 216, Everyman's Library Edition. 



