 During the voyage Darwin investigated small invertebrates, while collecting specimens of other creatures for experts to examine and describe once "Beagle" had returned to England.More than half of his carefully organised zoology notes deal with marine invertebrates, and the notes record closely reasoned interpretations of what he found about their complex internal anatomy while dissecting specimens under his microscope, and of little experiments on their response to stimulation.His onshore observations included intense, analytical comments on possible reasons for the behaviour, distribution, and relation to their environment of the creatures he saw.