Eye-spots 53 



vast periods of time, appear to demand the inter- 

 vention of some more specific mode of energy 

 than that implied in the hypothesis of the sur- 

 vival of the fittest. We seem to require the aid 

 of some definite and persistent underlying force 

 which has gradually moulded the living matter 

 of these structures into forms adapted to re- 

 ceive, and modify the different kinds of energy 

 acting on them, so that it becomes capable of 

 stimulating corresponding centres of nervous 

 matter into purposive action. We can best 

 illustrate our meaning by referring to the 

 development of visual sensory organs. 



The simplest known form of an organic 

 visual apparatus is that of an " eye-spot," such 

 as exists in Euglena, a unicellular being con- 

 stituting a link between animals and plants. 

 Near the anterior end of the cell forming one 

 of these beings a bright red spot exists, which 

 consists of a meshwork of sensitive protoplasm 

 containing a number of red particles. Exter- 

 nally this spot is covered by one or more 

 granules adapted to receive, and concentrate 

 waves of light on the subjacent pigmented 

 sensitive mass. There can be no question as 



