There are no intermediate forms.

Some of the signatures are in the 'old style' and some in the 'new,' but there are none that are half and half.

So that, to repeat: We have here two types of signature, very much alike, but distinguishable.

They alternate, but do not merge into one another to produce intermediate forms.

The change occurs abruptly, but shows no tendency to increase as time goes on; it is not a progressive change.