A torus with a hole that can eat another torus. The transformation is continuous, and so can be achieved by stretching only without tearing or making new holes in the tori.
Torus Cannibal
See also
TorusExplore with Wolfram|Alpha
References
Antonov, A. A. "The Torus Cannibal." http://www.imm.dtu.dk/~uniaaa/animtorcan.gif.Gardner, M. The Colossal Book of Mathematics: Classic Puzzles, Paradoxes, and Problems. New York: W. W. Norton, pp. 263 and 267-269, 2001.Gardner, M. Penrose Tiles and Trapdoor Ciphers... and the Return of Dr. Matrix, reissue ed. New York: W. H. Freeman, 1989.
Referenced on Wolfram|Alpha
Torus CannibalCite this as:
Weisstein, Eric W. "Torus Cannibal." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/TorusCannibal.html