A superb series of photographs follow lion cubs Leo and Linda from the incubator stage at their zoo to the point where they are big enough to move into the cage next to their regal and roaring parents. (The cubs' relative size ranges here from under 4 lbs. to a little more than the capacity of a vertical file drawer.) If there is anything more photogenic than kittens it is probably lion cubs, although Tiger Tom, a contemporary playmate of this pair, might give them run for their money in a Beautiful Baby contest. The cameras of zoo director Marlin Perkins (of the noted TV shows Zooparade and Wild Kingdom) and his wife, atch the cubs at the right moments in their roughhouse, tumbling play. The text is made up of short captions as spoken by Leo, repeating and/or explaining the actions shown in the pictures. Print is large, vocabulary easy. Purrfectly delightful.