This is Massuet's conjectural emendation of the text, viz. archetypum for arcætypum. Grabe would insert per before arcæ, and he thinks the passage to have a reference to 1 Pet. iii. 20. Irenæus, in common with the other ancient fathers, believed that the fallen angels were the "sons of God" who commingled with "the daughters of men," and thus produced a race of spurious men.