A light, easy, nicely handled interlude with fourth-grade science enthusiast Alice and her current enthusiasm, a pet boa constrictor. When Alice first announces her plan, her parents give in because they don't expect her to save up enough allowance to realize it. (Her science teacher's boa cost $85.00.) But Alice finds a cut-rate boa (""not breeding stock"") for $25.00 plus $10.00 for the cage and sets out to earn the money. Inventors, she hears, make money; but though a rainy Saturday seems ""a perfect day to stay indoors and invent something,"" and though she keeps a careful record of each ingredient on her Paddington stationery, her furniture-polish invention (with chocolate syrup for a nice rich color) proves disastrous for the dining room table. Her mother puts a stop to her flute-playing begging act, with little sister Beatrice got up as a waif, but Alice finally hits upon a low-price popcorn sale outside the movie theater on Saturday afternoon--and the boa, Sir Lancelot, is hers. Alice's show-and-tell presentation wins her (and, at Alice's insistence, her best friend Sarah) membership in the snobbish fourth-grade ""Peaches"" clique (they call non-members Turnips); and Lancelot also scares away some older bullies who chase neighbors Peter and James home from school. Of course he also gets out of his cage one time, upsetting a business deal by settling down in Alice's father's golf bag; but then--the authors just seem to be tossing in incidents by this time--he catches a midnight burglar by wrapping himself around the intruder's neck. Just when Adams and Coudert seem to be tiring of Sir Lancelot, Alice does too; she's into molds now and sells her pet to Peter. Which is fine, for while the project lasts readers will be as fascinated with Lancelot as Alice's classmates, and as impressed by Alice's mastery of her pet and her subject.