8^ EVOLUTION AND NATURAL THEOLOGY. 



brata ;* while the eyes of the Annulosa, though 

 analogous in function, and probably fully as 

 efficient } as those of the higher animals, are 

 not yet proved to be homologous with them. 

 It is true that the Mollusca and Vertebrata 

 are believed to have originated from a crea- 

 ture resembling the larval forms of some of 

 the Molluscoida ; but this will not account for 

 the close similarity of the sense-organs of the 

 higher forms, nor for the exact correspondence 

 in function between their eyes, and the very 

 differently formed eyes of the Annulosa. On 

 any theory of casual variation, the mathema- 

 tical probabilities against the occurrence of 

 such correspondences are practically infinite. 

 We are therefore compelled to admit either 

 that the common ancestor of the Mollusca and 

 Yertebrata must have possessed some innate 

 tendency to acquire analogous sense-organs, 

 or that the necessary modifications must have 

 been guided in one direction in these groups, 



* See Murphy, " Instinct and Intelligence," vol. i. p. 321, and Mivart, 

 " Genesis of Species," p. 74, etc. 



t Many observations have been recorded which appear to prove that 

 insects are fully capable of recognising colour as such as well as sounds ; 

 but it is certain that the same classes of sounds and colours ^ produce 

 different effects on different animals. 



