Irenæus is apparently the earliest writer who represents the Invocation of the Holy Ghost as the immediate act of consecration:  “We make an oblation to God of the bread and the cup of blessing, giving Him thanks for that He has commanded the earth to bring forth these fruits for our nourishment.  And then, having completed the oblation, we call forth (ἐκκαλοῦμεν ) the Holy Spirit, that He may exhibit this sacrifice, both the bread the Body of Christ, and the cup the Blood of Christ, in order that the partakers of these antitypes may obtain the remission of sins and life eternal Frag. xxxviii..”