Charles F. Rousselet was an English microscopist and authority on rotifers (microscopic multicellular animals found mainly in fresh water). He resided in London. Between 1889 and 1900 he published some 30 papers, most of them in the Journal of the Quekett Microscopical Club. In his first paper he described a small portable binocular microscope (1889), while two of his later papers also dealt with advances in microscopy. However, most of his papers dealt with rotifers, providing lists and descriptions of new species and discussing their preservation and sense of vision.
Rousselet became a member of the British Association for the Advancement of Science in 1905. That same year he came to South Africa to attend the joint meeting of the British and South African Associations for the Advancement of Science during August and September, and accompanied a group of delegates on an excursion to the Victoria Falls. The tour ended in Beira, Mozambique, from where they returned to England. Whenever the opportunity arose Rousselet collected samples of water in which he searched for rotifers with his folding binocular microscope. Despite his tight schedule and the fact that most of southern Africa was experiencing its dry season, he managed to collect rotifers at Cape Town; Johannesburg; Pretoria; Tweespruit and Sannaspos in the Free State; Kimberley; and in Zimbabwe at Bulawayo, the Matoppo Hills, Victoria Falls, and the Hunyani River near Harare. At Victoria Falls he furthermore collected a fresh-water sponge that was described as a new species by R. Kirkpatrick* and named Spongilla rousseleti after the collector. During the return journey along the African east coast and in the Mediterranean he made daily collections of plankton from the sea.
Upon his return to London Rousselet described his trip and his finds in a paper, "Contribution to our knowledge of the Rotifera of South Africa", published in the Journal of the Royal Microscopical Society (1906). He was able to list 156 species of rotifers known from southern Africa at that time. Two years later he published a Note on the rotarian fauna of Boston (London, 1908). After some years he again turned his attention to the fauna of southern Africa, contributing a note, "On a collection of Rotifera from Natal" to the Annals of the Durban Museum (1914-1917, Vol. 1, p. 159).