Rev. Father John A. H. Slag, rector of St. Mary’s procathedral, will preach a sermon on Rome at the 10:30 o'clock mass Sunday morning, it was an nounced today. Father Slag recently returned from a four-month trip abroad during which he visited the Holy City and had an audince with the pope. He is expected to talk on other phases of his trip on subsequent Sundays. Members of the Knights of Colum bus are planning a breakfast recep tion for Father Slag to be held on Sunday morning, August 31, probably in the Lions room at the Grand Pa cific hotel.