FIG. 47.--The Laboratory of the Marine Biological Association on the Citadel Hill, Plymouth 155 FIG. 48.--The Tsetze fly, _Glossina morsitans_ 172 FIG. 49.--The Trypanosome of Frog’s blood 173 FIG. 50.--The Trypanosome which causes the Sleeping Sickness 176 FIG. 51.--The Trypanosome of the disease called “Dourine” 177 FIGS. 52 to 56.--Stages in the growth and multiplication of a Trypanosome which lives for part of its life in the blood of the little owl, _Athene noctua_, and for the other part in the gut of the common Gnat (_Culex_) 180-3 PREFACE _This little volume is founded on three discourses which I have slightly modified for the present purpose, and have endeavoured to render interesting by the introduction of illustrative process blocks, which are described sufficiently fully to form a large extension of the original text._ _The first, entitled ‘Nature’s Insurgent Son,’ formed, under another title, the Romanes lecture at Oxford in 1905. Its object is to exhibit in brief the ‘Kingdom of Man,’ to shew that there is undue neglect in the taking over of that possession by mankind, and to urge upon our Universities the duty of acting the leading part in removing that neglect._ _The second is an account, which served as the presidential address to the British Association at York in 1906, of the progress made in the last quarter of a century towards the assumption of his kingship by slowly-moving Man._ _The third, reprinted from the_ Quarterly Review, _is a more detailed account of recent attempts to deal with a terrible disease--the Sleeping Sickness of tropical Africa--and furnishes an example of one of the innumerable directions in which Man brings down disaster on his head by resisting the old rule of selection of the fit and destruction of the unfit, and is painfully forced to the conclusion that knowledge of Nature must be sought and control of her processes eventually obtained. I am glad to be able to state that as a result of the representations of the Tropical Diseases Committee of the Royal Society, and, as I am told, in some measure in consequence of the explanation of the state of things given in this essay, funds have been provided by the Colonial Office for the support of a professorship of Protozoology in the University of London, to which Mr. E. A. Minchin has been appointed. It is recognized that the only way in which we can hope to deal effectually with such diseases as the Sleeping Sickness is by a greatly increased knowledge of the nature and life-history of the parasitic Protozoa which produce those diseases._