Second metamorphosis for well-known actor; Houseman at peak, Final Dress, by John Houseman. New York: Simon & Schuster. 559 pp. $19.95.

According to John Houseman, there have been two major metamorphoses in his long and adventurous life. The first occurred in the 1930s, ''when Jacques Haussmann, the hybrid, halfhearted European grain merchant, was transformed into John Houseman, a rootless, desperate novice in American show business'' and a new American citizen. Half a century later, the second metamorphosis ''marked my transformation from a respected but neglected veteran in the American theatre to one of the most sought-after and highly-paid aging male performers in the mass media.''

Indeed, Mr. Houseman has received more public recognition for his Oscar-winning Professor Kingsfield of ''The Paper Chase'' and its subsequent TV spinoffs than for all the other accomplishments of his 50-year career; add another entry to the irony file. Mr. Houseman deals with the phenomenon in a postscript to ''Final Dress,'' his third volume of memoirs.

The two earlier autobiographical installments, ''Run-through'' and ''Front and Center,'' covered the earlier decades of the long transformation. ''Final Dress'' carries the Houseman saga forward to 1974. It is a fascinating account by an extraordinarily versatile writer, producer, director, educator, and now actor, who seems to have been happiest when juggling two projects simultaneously.

A pair of themes counterpoint each other in ''Final Dress'' (a theatrical phrase referring to the last dress rehearsal before public performances begin). One theme has to do with the struggles and successes, disappointments and failures of a determinedly competitive showman for all media. The other theme concerns Mr. Houseman's longstanding commitment to the creation of a permanent repertory theater - an acting ensemble appearing in a changing program of classic and modern plays.

Like the two volumes that have preceded it, ''Final Dress'' enumerates the rewards, frustrations, and heartbreaks experienced in pursuing such an idea. Mr. Houseman has been associated as a founding father and-or guiding spirit of no less than six nonprofit institutional theaters. These have included two Works Progress Administration projects, the Mercury Theatre (with the mercurial Orson Welles), the American Shakespeare Festival Theatre and Academy (Stratford, Conn.), the UCLA Professional Theatre Group, the APA-Phoenix, and the Acting Company. The last-mentioned troupe, founded in 1972 from the first graduating class of the Juilliard Music School's drama division, is still going strong with Mr. Houseman as its producing artistic director.

Of all his many and diverse activities as a man of the theater, Mr. Houseman's role as founding director of Juillard's drama division may prove the most substantial and far-reaching. Its accomplishments have been exceptional. Its long-term significance is immeasurable. Juilliard appropriately occupies the front-and-center position in six of the most absorbing chapters of ''Final Dress.'' Mr. Houseman guides the reader from the preparatory stages - with the inspiring participation of Michel Saint-Denis and his wife, Suria - through the formative, initial four years and the debut of what came to be known as the Acting Company.

Being a playmaker's memoir, ''Final Dress'' recalls a variety of pleasant, prickly, difficult, and even impossible associations. Among the most vividly chronicled collaborations are those with Martha Graham on her memorable TV series; Henry Fonda on ''Clarence Darrow''; Katharine Hepburn and director Jack Landau at Stratford, Conn.; and Jean Rosenthal, the brilliant lighting and technical director on so many Houseman productions.

In recording press and public response to the works with which he has been connected, the author presents what appears to be a fair balance between pros and cons. Of his many colleagues in the precarious business of pleasing the public, he is more often appreciative than condemning. Some of his tributes are eloquent. In the more personal sections of the book, he is reasonably candid about his own faults and shortcomings.

And so back to the acerbic but deeply concerned Professor Kingsfield. Shortly after a pre-release screening of ''The Paper Chase'' for his drama-division students, Mr. Houseman found them coolly noncommital about his part in the picture. When his actor's vanity could no longer stand the silent treatment, he asked a group of them what they had thought about his performance.

''Performance?'' they said. ''That was no performance. That's the way you behave around here.''