Protozoa inhabiting the rumen of large grazing animals can be used to illustrate symbiotic animal associations. Gives a key to the ciliates most commonly found, several drawings, and a chart relating rumen fauna to the phylogenetic tree of the hosts. (EB)

A simulation exercise involving being transported to another planet forces students to use different instruments, devices, and units for measuring. (CP)

Describes an undergraduate optics laboratory experiment to verify the law of intensity in the Fesnel diffraction of a thin wire. A gas laser as light source and a photocell as detector scan the diffraction pattern. The agreement with the theoretical pattern is remarkably good. (Author/TS)