Now in development: The WB III — The Next Generation.

The WB’s evolution can be chopped up into three different phases, with the third — under net chairman Garth Ancier and entertainment prexy David Janollari — just getting under way.

In many ways, chapter three may be the most difficult of the WB’s short life. Ten years after its launch, the net has matured to a point where it can no longer count on major new distribution channels or early network adopters to expand its reach. In other words, the net will live or die almost solely on its content.

Adding to the monumental shift: The WB is entering its second decade without several of its original architects, including founder Jamie Kellner, former chief operating officer Jed Petrick and ex-entertainment topper and CEO Jordan Levin.

“This is no longer a start-up,” Ancier says. “This is a fully established company. That always means a change in direction, taking a mature asset and repopulating it with new shows. That’s what David Janollari and his team are charged with doing now. And hopefully we’ll have huge success next fall.”

Of course, the Frog has made it to a point far beyond what many would have predicted when the net launched in 1995.

“I was across the lot at Warner Bros. TV when news trickled over that a network was being started,” remembers Janollari. “We all in town were going, ‘Huh? Can that be done? Are they crazy? There are already four networks.’ But now there are not only six networks, but so many cable outlets as well.”

The WB’s early days were rough, as the net raced to get on the air and launched a critically reviled roster of urban-themed comedies, including shows such as the long-forgotten “Muscle,” as well as early staples “The Wayans Bros.” and “Unhappily Ever After” (both of which made it into syndication).

“It was not your dream schedule,” Kellner admits, “but once we got on the air, we had more lead time to develop more programs.”

Ancier says the net wound up launching with comedies because they take just seven months to get on the air, while dramas require more lead time.

“And we had to be on the air the same week as UPN,” he recalls. “We only had X amount of months. We had to do young-oriented sitcoms and urban sitcoms because our strongest stations were in the urban areas.”

After that, the WB entertainment team got down to business. The short-lived sudser “Savannah” gave the Frog some early notice, while drama “7th Heaven” gave the WB a surprise hit — and a reason to make a concerted push into developing more family-oriented fare.

“All of us who had done this before had become known as the ‘Bad Boys of Fox,’ the guys who would put on ‘Married With Children,’ ” Ancier says. “We realized we had to stay young but we couldn’t clone Fox — that was their identity — so we had to do something different.”

That meant tapping into a family audience that had been neglected by the major webs. Beyond “7th Heaven,” shows like “Smart Guy” and “The Steve Harvey Show” went after young viewers and their parents.

“No network was putting on ‘7th Heaven,’ ” Ancier says. “They weren’t putting on family product.”

But that was just the prelude. As young viewers started to discover the WB, the net expanded the definition of “family programming” with the smart, youth-oriented sudser “Dawson’s Creek” and the clever thriller “Buffy the Vampire Slayer.” (It helped that a Sinclair affiliation switch had suddenly expanded the WB’s reach tenfold.)

Suddenly the network had arrived and under the creative direction of Levin and fellow former entertainment prexy Susanne Daniels, had found its groove.

The launch of “Dawson’s Creek” in January 1998 ushered in a second wave for the WB and made the network a real player for younger eyeballs. Suddenly creative types wanted to develop for the scrappy network. And through countless magazine covers and other media attention, the Frog had garnered “it” status.

“We were all so competitive we never looked at failure as an option,” Ancier says. “But the moment we felt (that the network had arrived) and the public felt that way was when ‘Dawson’ premiered. The show was on four multiple covers of TV Guide and immediately had a huge cultural impact.”

Hits such as “Felicity,” “Charmed,” “Smallville,” “Gilmore Girls” and countless others came at breakneck speed in the years that followed.

Meanwhile, on the exec front, until recently the WB had prided itself on harboring one of the most stable executive teams in network TV. But change is one of the few constants in network TV and the WB has been no exception.

Slowly, the net’s exec roster changed, as Ancier left to lead NBC Entertainment. Daniels later departed, and Kellner expanded his oversight to include Turner.

Kellner retired last year and handed the network reins to Levin and Ancier (who had since returned) but Warner Bros. brass Barry Meyer and Bruce Rosenblum opted to mix things up soon after.

With the departure of execs like Kellner and Levin — as well as the end of “Dawson” and most of the WB’s other original hits — Ancier and newcomer Janollari are now figuring out the blueprints for the Frog’s third incarnation.

The foundation’s still there thanks to more recent hits such as “One Tree Hill” and “Reba.” Now the net must figure out what a WB series looks like in 2005.

“There are a number of fantastic, long-running shows on our network,” Janollari says, “but ultimately every show doesn’t go on forever. As we see some shows head into their seventh, eighth and ninth years, we have to prepare for the future. Our priority No. 1 is finding those next big hits.”