144 DIFFICULTIES OF THE THEORY [CHAP. VL 



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 through- 

 out 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 Xucula 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 

 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, 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 fertilisation. With several 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 conceived. An almost equally 

 simple, though very different, plan occurs in many plants in which 

 A symmetrical flower secretes a few drops of nectar, and is con- 

 sequently 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 

 receptacles, with the stamens and pistils modified in many ways, 

 sometimes forming trap-like contrivances, and sometimes capable 

 of neatly adapted movements through irritability or elasticity. 

 From such structures we may advance till we come to such a case 

 of extraordinary adaptation as that lately described by Dr. Criiger 

 in the Coryanthes. This orchid has part of its labellum or lower 

 lip hollowed out into a great bucket, into which drops of almost 



