In Bullfrog Grows Up (1976), we saw Bullfrog, adopted as a tadpole, bidding good-bye to the mouse family whose home he had outgrown. Bullfrog Builds a House (1977) ended with his inviting fellow bullfrog Gertrude to share his new home. Here the two go camping and run into a lonesome snake. ""It's a snake,"" says Gertrude, so It's a Snake becomes the stranger's name. Bullfrog is annoyed when Itsa tries to climb into his sleeping bag, but grateful when the snake warns him of poison ivy. Another sad parting (sad at least for Itsa) seems in store as the camping trip ends. But Gertrude is gently persuasive--""But Bullfrog, you were adopted by the Mouse family""--and this ends with the new family of three walking happily homeward. In itself, the story is a shade less substantial than its predecessors, but it shows the same gently offbeat touch. As a sequel, it's irresistible.