Can a kitten grow up to be a mouse? Naturally not, and it's hard from the start here to accept the foundling Kittenmouse as the sibling of mice children Tilly, Milly, and Max even though--in a separate bit of incongruity--the mice are daintily dressed. The chief problem of Mr. and Mrs. Mouse, of course, is to keep Kittenmouse from discovering she's a cat--but as soon as she hears her first ""Meow"" and has her first sip of milk, the truth will out. ""I can see the time has come to tell you who you really are,"" sighs Mrs. M.--suddenly aware that her complacently adopted child will soon outgrow a, mousehole. The resolution has Kitten-mouse happily sharing her affections with her human and her mouse family--and the latter, thanks to her, forever untroubled by cats. Maybe, indeed, this kitten does grow up to be something of a mouse--or at any rate, no properly independent feline. The pictures are quite accomplished in an undistinguished, Paul-Galdone way; the story's a passing fancy.