The author recommends the incubation of chicken eggs as a worthwhile learning experience and suggests procedures. (CP)

Short articles on a demonstration of enzyme action, models of mammalian circulatory systems, measuring the height of trees, the ecology of the African amphibian Xenopus under natural conditions in England, experiments with liverwort gemmae, investigations using stick insects, and a culture medium for Paramecium bursaria. (AL)

Short articles describe the demonstration of Brownian motion in a bubble included in a quartz crystal, an inexpensive technique for investigating conservation of momentum, a method of teaching vector addition, and ideas for inexpensive substitutes for heavy masses and for additional laboratory bench space. (AL)

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)