RUDIMENTARY ORGANS 267 



ancy, but has become converted into a nascent breathing 

 organ or lung. Many similar instances could be given. 



Useful organs, however little they may be developed, 

 unless we have reason to suppose that they were formerly 

 more highly developed, ought not to be considered as 

 rudimentary. They may be in a nascent condition, and 

 in progress toward further development. Kudimentary 

 organs, on the other hand, are either quite useless, such 

 as teeth which never cut through the gums, or almost 

 useless, such as the wings of an ostrich, which serve 

 merely as sails. As organs in this condition would for- 

 merly, when still less developed, have been of even less 

 use than at present, they cannot formerly have been 

 produced through variation and natural selection, which 

 acts solely by the preservation of useful modifications. 

 They have been partially retained by the power of in- 

 heritance, and relate to a former state of things. It 

 is, however, often difficult to distinguish between rudi- 

 mentary and nascent organs; for we can judge only 

 by analogy whether a part is capable of further devel- 

 opment, in which case alone it deserves to be called 

 nascent. Organs in this condition will always be some- 

 what rare; for beings thus provided will commonly have 

 been supplanted by their successors with the same organ 

 in a more perfect state, and consequently will have be- 

 come long ago extinct. The wing of the penguin is of 

 high service, acting as a fin; it may, therefore, represent 

 the nascent state of the wing: not that I believe this to 

 be the case; it is more probably a reduced organ, modi- 

 fied for a new function: the wing of the Apteryx, on 

 the other hand, is quite useless, and is truly rudimen- 

 tary. Owen considers the simple filamentary limbs of the 



