Which English naturalist traveled to Stonehenge to conduct research on earthworms?

In 1877, naturalist Charles Darwin (1809-1882) travelled to Stonehenge to conduct research on earthworms. He was interested in the impact that worms had on objects in the soil over time. He observed that a fallen stone at the ancient monument had sunk deeper into the ground as a result of the activities of the earthworms that continually churned through the soil under the fallen stone.

Darwin’s research was included in his final book, ‘The Formation of Vegetable Mould Through the Action of Worms, with Observations on their Habits’, published in 1881. This was his last scientific book, published shortly before his death. It was the first significant work on soil ‘bioturbation’ (defined as the reworking of soils and sediments by animals or plants), although that term was not used by Darwin and didn’t appear in the professional literature until 100 years later. The first edition of Darwin’s publication included 326 pages.

Each of the other individuals listed were also English naturalists- Henry Baker (1698-1774), William Andrews (1802-1880), and Sidney Collingwood (1826-1908).