Rudd Weatherwax, 77, who spent $10 to purchase an unwanted collie and trained it and a series of successors into an American acting legend called "Lassie," died of a respiratory ailment Feb. 25 at a hospital in Mission Hills, Calif.

In addition to six generations of "Lassies" who spanned more than 30 years, Mr. Weatherwax trained hundreds of other animals. His canine characters included "Asta," the terrier who played in the immensely popular "Thin Man" film series starring Myrna Loy and William Powell; "Daisy," who romped through the "Blondie" movie series, and the star of "Old Yeller," a classic film in which a boy has to shoot his faithful dog after it contracts rabies.

But it was "Lassie" who gained him his real fame and fortune. That began when Mr. Weatherwax bought a dog named "Pal" for $10. "Pal" was selected from among hundreds of candidates to play the title role in the 1943 film, "Lassie Come Home," which also starred Elizabeth Taylor and Roddy McDowall.

The film led to sequels and eventually a television series that ran on Sunday nights on the CBS network from 1954 to 1971. Unlike the supporting cast, which at various times included Tommy Rettig, Jon Provost, Cloris Leachman and June Lockhart, "Lassie" never changed: the best doggone friend a man, woman or child ever had.

The dog got a new master every few years. Other characters had more foibles than virtues and some were downright mean. "Lassie" became a symbol of love and loyalty and this was a key ingredient in the enduring popularity of the show.

Typically, the dog cared for people rather than the other way around. It lived with farm families and forest rangers and saved countless lives and prevented untold disasters and suffering. But in a seven-part series in the fall of 1970, the last season of the television program, "Lassie" became a wanderer, seemingly giving up her career of protecting human-kind, and finding love.

She met a collie and bore a litter of pups. This required an extra willingness to suspend disbelief because that "Lassie," like all previous "Lassies," was a male. Male collies are believed to have more luxurious coats and greater stamina than females. But Mr. Weatherwax took no chances. He insured at least one of his stars for $1 million and trained and used stunt doubles for the star of the moment.

Mr. Weatherwax grew up on a ranch in New Mexico, where he first raised and worked with collies. His father used the dogs to herd his flock of 3,500 Angora goats. The family moved to Los Angeles in 1917.

At the age of 14, Mr. Weatherwax got into show business. He got his pet fox terrier a part in a movie that featured a four-footed telegram messenger. The rest, as they say, is history.

Mr. Weatherwax's survivors include a son, Robert, and a daughter, Joann Curtis, both of Canyon Country, Calif.; two brothers, Frank, of Malibu, Calif., and William, of Van Nuys, Calif.; five grandchildren, and one great-grandchild.