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 Ornithorhynchus 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.