The Ridgefield man accused of beating his mother with a baseball bat has pleaded not guilty.  According to court records, 21-year old Colin Donnelly was charged with assault.  He entered the plea Thursday in Danbury Superior Court and was ordered back in court on January 21st.  He allegedly attacked the 55-year-old woman inside their Peaceable Street home on November 15th.  The victim was transported to Danbury Hospital with what were said to be serious injuries.