For my own part, I think it decidedly the more probable hypothesis that he used our present Gospels with some peculiar document, such as this Gospel according to the Hebrews, or perhaps, as Dr.Hilgenfeld thinks, the ground document of the Gospel according to Peter (a work of which we know next to nothing except that it favoured Docetism and was not very unlike the Canonical Gospels) and the Protevangelium of James (or some older document on which that work was founded) in addition.
It will be well to try to establish this position a little more in detail; and therefore I will proceed to collect first, the evidence for the use, either mediate or direct, of the Synoptic Gospels, and secondly, that for the use of one or more Apocryphal Gospels.

We still keep to the substance of Justin's Gospel, and reserve the question of its form.
Of those portions of the first Synoptic which appear to be derived from a peculiar source, and for the presence of which we have no evidence in any other Gospel of the same degree of originality, Justin has the following: Joseph's suspicions of his wife, the special statement of the significance of the name Jesus ('for He shall save His people from their sins,' Matt.i.21, verbally identical), the note upon the fulfilment of the prophecy Is.

vii.
14 ('Behold a virgin,' &c.), the visit of the Magi guided by a star, their peculiar gifts, their consultation of Herod and the warning given them not to return to him, the massacre of the children at Bethlehem, fulfilling Jer.xxxi.15, the descent into Egypt, the return of the Holy Family at the succession of Archelaus.

The Temptations Justin gives in the order of Matthew.
From the Sermon on the Mount he has the verses v.

14, 20, 28, vi.
1, vii.