Discovering what earthworms do involves many observations miscalled experiments and some quasi-experiments that prove very little (which kinds of leaves an earthworm prefers, and whether your findings jibe with an expert's list), others that are of dubious justification (cutting up earthworms at various points to see how they regenerate). The book assumes that the child will be able to watch earthworms at night, after a rain, etc. and be able to keep some at hand; the first is difficult in the city, the second is hampered here by slipshod instructions. In this area, as in most others, the Dorothy Hogner Earthworms is more precise and methodical (the Simon lacks even a diagrammatic illustration of the earthworm's interior; it also fails to identify types). Only in regard to mating, which Hogner omits, does this have an edge.