AND ABORTED ORGANS. 441 



successors with the same organ in a more perfect state, and 

 consequently will have become 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, modified for a new function ; the wing of the Apteryx, 

 on the other hand, is quite useless, and is truly rudimentary. 

 Owen considers the simple filamentary limbs of the Lepido- 

 siren as the " beginnings of organs which attain full func- 

 tional development in higher vertebrates ; " but, according 

 to the view lately advocated by Dr. Giinther, they are prob- 

 ably remnants, consisting of the persistent axis of a fin, 

 with the lateral rays or branches aborted. The mammary 

 glands of the Ornithorhynchus may be considered, in com- 

 parison with the udders of a cow, as in a nascent condition. 

 The ovigerous frena of certain cirripedes, which have ceased 

 to give attachment to the ova and are feebly developed, are 

 nascent branchiae. 



Rudimentary organs in the individuals of the same species 

 are very liable to vary in the degree of their development 

 and in other respects. In closely allied species, also, the 

 extent to which the same organ has been reduced occasion- 

 ally differs much. This latter fact is well exemplified in 

 the state of the wings of female moths belonging to the 

 same family. Rudimentary organs may be utterly aborted ; 

 and this implies, that in certain animals or plants, parts are 

 entirely absent which analogy would lead us to expect to 

 find in them, and which are occasionally found in monstrous 

 individuals. Thus in most of the Scrophulariacea? the fifth 

 stamen is utterly aborted ; yet we may conclude that a fifth 

 stamen once existed, for a rudiment of it is found in many 

 species of the family, and this rudiment occasionally becomes 

 perfectly developed, as may sometimes be seen in the com- 

 mon snap-dragon. In tracing the homologies of any part in 

 different members of the same class, nothing is more common, 

 or, in order fully to understand the relations of the parts, 

 more useful than the discovery of rudiments. This is well 

 shown in the drawings given by Owen of the leg bones of 

 the horse, ox and rhinoceros. 



It is an important fact that rudimentary organs, such as 

 teeth in the upper jaws of whales and ruminants, can often 

 be detected in the embryo, but afterward wholly disappear. 

 It is also, I believe, a universal rule, that a rudimentary 

 part is of greater size in the embryo relatively to tfc§ 



