"It was great to represent England against the Barbarians last season, and then to be involved in the Churchill Cup squad, and those experiences gave me a taste for more," said Mears.
"I have worked hard on my game over the past couple of seasons, and Mike Foley (Bath coach) has really helped me to that end.
"This is a good opportunity for me, and comes as a big boost ahead of a new campaign with Bath."
Farrell now finds himself in England company, just five months after switching codes and with his union debut still on ice.
He joined Saracens from Wigan earlier this year in a six-figure deal jointly funded by his new club and the Rugby Football Union.
Farrell is expected to feature in the centre or back-row for Saracens, and could make his debut during the club's pre-season schedule, which includes friendlies against Bedford on August 20 and Quins seven days later.
Only three of England's original 19-strong Lions contingent are not included. Neil Back and Lawrence Dallaglio have both retired from international rugby, while flanker Richard Hill is currently battling a career-threatening knee injury.
England head coach Andy Robinson though, has scope to increase his senior squad by a further five players and add another four to a current 16-man senior academy group, but he will not call up any more than 30 at a time for England training days or Test weeks, following an agreement reached between the RFU and Premier Rugby.
"These 61 players in the senior squad and senior national academy will form the back-bone of our England hopes and aspirations for the coming season, and we are able to add one or two more to the list to a maximum 70, depending on form and recovery from injury," said Robinson.
"In the next few weeks, I plan to call up no more than 30 players at any given time, predominantly from the senior squad, for England training days that have been agreed in principle with their clubs, and for Test weeks."