In Saturday's editorial, "The Democrats So Far . . ." we said the Democrats gained House seats last November. In fact they lost seats.

The Democrats, so long now out of power in the rest of the federal government, remain very much in control of the House of Representatives. There position there is firmer than ever. A year ago they were on the defensive on the floor and on the hustings. But they gained seats last November and have, in the course of this year, gained a considerable amount of initiative as well. As House members leave town to face the voters, there's no doubt that it's the Democrats who have the esprit and the Republicans who are in the doldrums.

This is noteworthy for two reasons. First, the Democrats' majority in not as large as those that have enabled them to control the House in the past. But there have been fewer defections and there is more unity. The perception is widespread that Speaker O'Neill and the leadership stand for big-government programs and are hostile to the South and West. But Mr. O'Neill was at least careful to include the Boll Weevils in the budget deliberations, and he hasn't been caught backing any new big-government programs lately. The Democrats, in their last session in Washington, have been showing unaccustomed unity.

The second noteworthy thing is that, even though the Democrats are the out party, they have approached issues constructively. You can overstate this, of course. The budget budget resolution that the House Democrats passed was late, included a number of illusory cuts and is without enforcement mechanisms. But it was better than no budget resolution at all, and better than what was expected. Moreover, the appropriations bill the Democrats have been passing have stayed within the limits of their budget resolution -- a welcome and not always politically easy course.

There are things on the other side of the balance. The House Democrats have shamelessly used Social Security as a political issue, and they seem embarked, as part of a 1986 campaign strategy, on using the trade issue in a particularly irresponsible manner. Like the Republican Senate, they're having a hard time patching together a farm bill, and they've taken some craven and hysterical stands in response to the genuine concern everyone has about espionage.

We are in the fifth year of divided control of the Congress. It occurred quite unexpectedly, but to some it has come to seem the natural order of things. How long it will continue no one is sure. But the House Democrats, pleased with their (relative) unity and (somewhat) constructive record, seem confident they will maintain and increase their hold on the House in the elections that are only 15 months away.