T9I7- Carpenter.— ?7.s^//^/ Studies for Field Naturalists. 67 



This evening the President cannot improve his voice 

 or the members their powers of hearing with these appli- 

 cations, but we can all recognize that Keogh's interest in 

 zoology was largely utilitarian, and it may be instructive 

 for us to trace the connection of some economic applications 

 of natural history with the cultivation of the science for 

 the sake of the interest and fascination which it has for us. 

 People often talk and write of " pure " and " applied " 

 science ; but as Huxley taught us long ago there are not 

 two kinds of science but one. It ma^^ be desirable to enter 

 a protest against two points of view both inimical to the 

 advancement of science among our people : firstly, the 

 supercilious outlook of some " pure scientists " who affect 

 to believe that a discovery is somehovv^ degraded if it become 

 useful to mankind ; and secondly, the intolerant attitude 

 of some " practical men " who would discourage any line 

 of research that cannot be clearly directed to an economic 

 issue. As a matter of fact enquiries undertaken — like 

 Keogh's — for the sake of miedicine or agriculture, often 

 yield results of high theoretical importance, while there is 

 no line of biological research that may not at some time 

 contribute to the preservation of human health or to the 

 advancement of human industry. 



The last twenty years have been noteworthy for a remark- 

 able advance in our knowledge of the parasitic Protozoa, 

 such as the Haemosporidia and the Haemoflagellata. The 

 researches that led to these discoveries were undertaken 

 bv medical men who worked at the life-histories of the 

 protozoan parasites in order that they might be the better 

 able to prevent or relieve disease in man and domestic 

 animals. In such practical results the investigations have 

 proved abundantly fruitful, but how impressive also has 

 been the progress of zoological science associated with them, 

 as illustrated for example by the elucidation of a true sexual 

 reproduction among the Protozoa and of the adaptation 

 of these minute parasites for a life in two alternate hosts — 

 the vertebrate and the blood-sucking gnat or tick. 



Some time ago I gave before this Club an account of the 

 progress made in an investigation into the life-history of 

 the Ox Warble-flies — an investigation with a definitely 



