I do not now allude to the presence in it of added traits, such as the cave of the Nativity and the fire on Jordan, which are of the nature of those mythical details that we find more fully developed in the Apocryphal Gospels.

I do not so much refer to these--though, for instance, in the case of the fire on Jordan it is highly probable that Justin's statement is a translation into literal fact of the canonical (and Justinian) saying, 'He shall baptize with the Holy Ghost and with fire'-- but, on general grounds, the relation which this supposed document bears to the extant Gospels shows that it must have been in point of time posterior to them.
The earlier stages of evangelical composition present a nucleus, with a more or less defined circumference, of unity, and outside of this a margin of variety.

There was a certain body of narrative, which, in whatever form it was handed down--whether as oral or written--at a very early date obtained a sort of general recognition, and seems to have been as a matter of course incorporated in the evangelical works as they appeared.
Besides this there was also other matter which, without such general recognition, had yet a considerable circulation, and, though not found in all, was embodied in more than one of the current compilations.

But, as we should naturally expect, these two classes did not exhaust the whole of the evangelical matter.
Each successive historian found himself able by special researches to add something new and as yet unpublished to the common stock.
Thus, the first of our present Evangelists has thirty-five sections or incidents besides the whole of the first two chapters peculiar to himself.

The third Evangelist has also two long chapters of preliminary history, and as many as fifty-six sections or incidents which have no parallel in the other Gospels.