402 SUMMARY". [Ciiap. XIV. 



effects of disuse, rudimentary and would at last be wholly sup- 

 pressed ; for the variations towards diminished size would no longer 

 be checked by natural selection. The principle of the economy 

 of growth, explained in a former chapter, by which the materials 

 forming any part, if not useful to the possessor, are saved as far as 

 is possible, will perhaps come into play in rendering a useless part 

 rudimentary. But this principle will almost necessarily be con- 

 fined to the earlier stages of the process of reduction ; for we cannot 

 suppose that a minute papilla, for instance, representing in a male 

 flower the pistil of the female flower, and formed merely of cellular 

 tissue, could be further reduced or absorbed for the sake of econo- 

 mising nutriment. 



Finally, as rudimentary organs, by whatever steps they may 

 Jiave been degraded into their present useless condition, are the 

 record of a former state of things, and have been retained solely 

 through the power of inheritance, — we can understand, on the 

 genealogical view of classification, how it is that systematists, in 

 placing organisms in their proper places in the natural system, have 

 often found rudimentary parts as useful as, or even sometimes more 

 useful than, parts of high physiological importance. Rudimentary 

 organs may be compared with the letters in a word, still retained 

 in the spelling, but become useless in the pronunciation, but which 

 serve as a clue for its derivation. On the view of descent with 

 modification, we may conclude that the existence of organs in a 

 rudimentary, imperfect, and useless condition, or quite aborted, far 

 from presenting a strange difficulty, as they assuredly do on the old 

 doctrine of creation, might even have been anticipated in accordance 

 with the views here explained. 



Summary. 

 In this chapter I have attempted to show, that the arrangement 

 of all organic beings throughout all time in groups under groups — 

 that the nature of the relationships by which all living and extinct 

 organisms are united by complex, radiating, and circuitous lines of 

 affinities into a few grand classes, — the rules followed and the. 

 difficulties encountered by naturalists in their classifications, — 

 the value set upon characters, if constant and prevalent, whether 

 of high or of the most trifling importance, or, as with rudimentary 

 organs, of no importance, — the wide opposition in value between 

 analogical or adaptive characters, and characters of true, affinity; 

 and other such rules ; — all naturally follow if we admit the common 

 parentage of allied forms, together with their modification through 

 variation and natural selection, with the contingencies of extinction 



