But last year's runners-up were only able to gain a one-point lead over their Border rivals thanks to a last-minute try from the Melrose prop Millan Browne, his side's fourth, which secured a bonus point.
Melrose got off to the perfect start with a try from the scrum-half Bryan Redpath, but the home side didn't take long to respond and tries by Jamie Mayer, Cammy Murray and Andy Garry helped Watsonians to a 26-14 half-time lead.
Melrose fought back after the restart, but all their good work was undone when Watsonians' Scotland Under-21 star Jamie Mayer grabbed his second try with six minutes remaining.
Glasgow Hawks, the runaway leaders of Division Two, continued their dominance with a 62-3 thrashing of Peebles. In their search for more testing opposition Glasgow have lined up a match against the Heineken Cup semi- finalists Toulouse at Old Anniesland this Friday.
Harlequins also have a French concern, but it is the loss of their fly- half Thierry Lacroix with a hamstring injury for today's Allied Dunbar Premiership match at Newcastle. If Quins lose it will be their worst run of successive league defeats since 1994.
Bedford increased their hold on the lead of Premiership Two with a 24- 13 win at Wakefield, after second-placed London Scottish were held 18- 18 at home by Coventry. Rotherham stay third after a 31-18 win at Blackheath.
In the Welsh National League Premier Division Pontypridd made the most of entertaining bottom-placed Newport with a 41-3 victory that secured enough bonus points to move level with Cardiff in second. Neath continued their resurgence with a tight 32-26 result at Bridgend.Reuse content