Spirit: Smooch and Winslow become convinced, in part by Madge, that the World Tree has a Spirit. With Snook's help, they set out to find it. Shell: Bob and Winslow are surprised that the rock they found isn't a rock but the shell of a snail named Rocky. At first Winslow wants a shell of his own, but he eventually learns that shells aren't right for Marmosets. EDUCATIONAL OBJECTIVES: Shells - Different creatures live in their own special places, and have different means of protection. Trees - Tree biology and facts.