Jon,
How about this source?
On the Eucharist
Luther regarded the Mass as an abomination, all the worse because at its heart was the most important of all Christian ceremonies: the re-enactment of the Last Supper. Luther stripped away all the extra rituals but left the core event, the taking of bread and wine. You will notice that both wine and bread were part of the Lutheran communion. He, like the Hussites, could find no Biblical justification for excluding the faithful from the full commemoration.
Very early on, however, the question was raised as to the nature of what transpired at communion. The Catholics taught that the bread and wine were, at the moment of the elevation of the Host, miraculously transformed by the Holy Ghost into the actual body and blood of Christ. This transformed substance retained the appearance of bread and wine, but its essence was truly changed. It was no longer bread and wine.
Luther rejected this, but he had some difficulty describing what exactly did happen. His position by about 1524 was that of
consubstantiation: that the bread remained bread, the wine remained wine, and the body and blood of Christ were present. Both were there together. Other reformers (e.g., Zwingli) argued that the bread remained only bread, the wine only wine, and that communion was only a commemoration and nothing more.
Luther would not go that far. For him, the communion meal had to retain its essentially miraculous nature.
idbsu.edu/courses/reformation/luther/23.shtml