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.

In closely allied species, also, the extent to which the same organ has been reduced occasionally differs much.