I must have been five years old when my grandfather showed me a book about prehistoric life illustrated with the paintings of Z. Burian. The first picture I saw had such impact that it formed the start of a lifelong interest in natural history. The painting showed life in the Cambrian seas, the Cambrian period starting 650 million years ago being the era of the early crustaceans, the trilobites. This wonderful impression of ancient life depicted several trilobites walking around on their many segmented legs. Above them floated a group of jellyfish.
Trilobites are long extinct but jellyfish still swarm the oceans.
Observing lifeforms such as jellyfish gives you a glimpse of this wonderful past. They are not so difficult to study and they have a very interesting lifecycle. To study them alive the best thing to do is try and capture them with a plankton net or try and grab the polyp stages from the growth you can find on rocks and on the poles in a harbour. They can be kept alive for many days when put in a glass container. One of the most interesting aspects about jellyfish is the fact that they have two life phases.