240 DIFFICULTIES OF THE THEORY [Chap. VL 



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

 pendages 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 wings 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 disseminated 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, and ren- 

 dered nutritious, as well as conspicuously 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 fur- 

 nished 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 diver- 

 sified 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 



