MUTUAL AFFINITIES OF ORGANIC BEINGS 407 



sails. As organs in this condition would formerly, when still less 

 developed, have been of even less use than at present, they cannot 

 formerly have been produced through variation and natural se- 

 lection, which acts solely by the preservation of useful modifica- 

 tions. They have been partially retained by the power of inherit- 

 ance, and relate to a former state of things. It is, however, often 

 difficult to distinguish between rudimentary and nascent organs; 

 for we can judge only by analogy whether a part is capable of 

 further development, in which case alone it deserves to be called 

 nascent. Organs in this condition will always be somewhat 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 become long ago extinct. The wing of the 

 penguin is of high service, acting as a fin ; it may, therefore, repre- 

 sent 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 Lepidosiren as the "beginnings of organs 

 which attain full functional development in higher vertebrates;" 

 but, according to the view lately advocated by Dr. GUnther, they 

 are probably remnants, consisting of the persistent axis of a fin, 

 with the lateral rays or branches aborted. The mammary glands 

 of the Omithorhynchus may be considered, in comparison 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 occasionally 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 Scrophulariacese 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 common 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 



