240 DIFFICULTIES OF THE THEOEY [Chap. VI. 



hind-legs, — of the maxillae or lips, — and of appendages 

 on the under side of the hind part of the body. 



In the foregoing cases, we see the same end gained 

 and the same function performed, in beings not at all 

 or only remotely allied, by organs in appearance, though 

 not in development, closely similar. On the other hand, 

 it is a common rule throughout nature that the same end 

 should be gained, even sometimes in the case of closely- 

 related beings, by the most diversified means. How 

 differently constructed is the feathered wing of a bird 

 and the membrane-covered wing of a bat ; and still more 

 so the four wiugs of a butterfly, the two wings of a fly, 

 and the two wings with the elytra of a beetle. Bivalve 

 shells are made to open and shut, but on what a 

 number of patterns is the hinge constructed, — from 

 the long row of neatly interlocking teeth in a Nucula 

 to the simple ligament of a Mussel! Seeds are dis- 

 seminated by their minuteness, — by their capsule 

 being converted into a light balloon-like envelope, — 

 by being embedded in pulp or flesh, formed of the most 

 diverse parts, ami rendered nutritious, as well as con- 

 spicuously coloured, so as to attract and be devoured by 

 birds, — by having hooks and grapnels of many kinds 

 and serrated awns, so as to adhere to the fur of 

 quadrupeds, — and by being furnished with wings and 

 plumes, as different in shape as they are elegant in 

 structure, so as to be wafted by every breeze. I will 

 give one other instance ; for this subject of the same 

 end being gained by the most diversified means well 

 deserves attention. Some authors maintain that 

 organic beings have been formed in many ways for 

 the sake of mere variety, almost like toys in a shop, 



