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.