DIFFICULTIES OF THE THEORY 157 



and in the several groups they are formed by the modification of 

 the fore legs, 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 con- 

 structed 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 rendered nutritious, as well as conspicuously colored, so 

 as to attract and be devoured by birds, by having hooks and grap- 

 nels 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, al- 

 most like toys in a shop, but such a view of nature is incredible. 

 With plants having separated sexes, and with those in which, 

 though hermaphrodites, the pollen does not spontaneously fall on 

 the stigma, some aid is necessary for their fertilization. With sev- 

 eral kinds this is effected by the pollen-grains, which are light and 

 incoherent, being blown by the wind through mere chance on to 

 the stigma; and this is the simplest plan which can well be con- 

 ceived. An almost equally simple, though very different plan oc- 

 curs in many plants in which a symmetrical flower secretes a few 

 drops of nectar, and is consequently visited by insects; and these 

 carry the pollen from the anthers to the stigma. 



From this simple stage we may pass through an inexhaustible 

 number of contrivances, all for the same purpose and effected in 

 essentially the same manner, but entailing changes in every part 

 of the flower. The nectar may be stored in variously shaped recep- 



