268 THE ORIGIX OF SPECIES 



Lepidosiren as the "beginnings of organs which attain 

 full functional development in higher vertebrates"; Init, 

 according to the view lately advocated by Dr. Giinther, 

 they are probably 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 comparison with the udders of a cow, 

 as in a nascent condition. The ovigerous frena of cer- 

 tain cirripeds, 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 spe- 

 cies, 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 or- 

 gans 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 Scrophulariaceae 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 spe- 

 cies of the family, and this rudiment occasionally be- 

 comes perfectly developed, as may sometimes be seen 

 in the common snap-dragon. In tr^fcing the homologies 

 of any part in different members of the same class, noth- 

 ing 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. 



