230 THE ORIUIS OF SPECIES 



Other. T am glad to tind that so liigh an authority as 

 Professor Flower has come to this same conclusion. 



The extraordinary cases given in a former chapter, of 

 widely different tishes possessing electric organs — of wide- 

 ly different insects possessing luminous organs — and of 

 orchids and asclepiads having pollen-masses with viscid 

 disks, come under this same head of analogical resem- 

 blances. But these cases are so wonderful that they 

 were introduced as difficulties or objections to our 

 theory. In all such cases some fuBdameotal difference 

 in the growth or development of the parts, and generally 

 in their matured structure, can be detected. The end 

 gained is the same, but the means, though appearing 

 superficially to be the same, are essentially different. 

 The principle formerly alluded to under the term of 

 analogical variation has probably in these cases often 

 come into play; that is, the members of the same class, 

 although only distantly allied, have inherited so much in 

 common in their corstitution that they are apt to vary 

 under similar exciting causes in a similar manner; and 

 this would obviously aid in the acquirement through 

 natural selection of parts or organs, strikingly like each 

 other, independently of their direct inheritance from a 

 common progenitor. 



As species belonging to distinct classes have often 

 been adapted by successive slight modifications to live 

 under nearly similar circumstances — to inhabit, for in- 

 stance, the three elements of land, air, and water — we 

 can perhaps understand how it is that a numerical paral- 

 lelism has sometimes been observed between the sub- 

 groups of distinct classes. A naturalist, struck with a 

 parallelism of this nature, bv arbitrarilv raising or sinking 



