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PREFACE. 



I HAVE attempted in the following monograph to give a concise and 

 accurate account of all the amoebae which live in human beings. 

 Although our knowledge of these protozoa has grown apace in the last 

 few years, there is at present — so far as I am aware — no published work 

 which gives a correct description of them from the standpoint of 

 modern protozoology. The works already published — the various 

 treatises on the Protozoa, and innumerable papers scattered through 

 zoological and medical periodicals — reveal, if taken together, a sad 

 state of confusion in the minds of men : and much that is now certainly 

 known appears uncertain, merely because of the conflicting and con- 

 tradictory statements with which the literature of this subject abounds. 

 That correct solutions of the chief problems of the past, and a true 

 account of the state of knowledge at present, would be welcomed by 

 many zoologists and medical men — especially by those whose work lies 

 in the tropics — I have good reason to believe: and it is in the hope of 

 contributing something towards the attainment of both these ends — the 

 clarification of ideas, and the codification of facts — that the following 

 pages have been written. 



This little treatise is addressed to all who are interested in the 

 amoebae of man from a zoological standpoint, and is intended for those 

 who already possess some acquaintance with the science of protozoology. 

 To these it is offered with the hope that the work which the author has 

 expended on it may lighten their labours in the same field. It is, more- 

 over, the work of a biologist and not of a medical man — of one whose 

 chief interest is, and has ever been, in the Protozoa themselves and not 

 in the diseases which they produce — of one whose point of view has 

 been determined not by practice as a physician but by the study of other 

 amoebae and their kindred. Few zoologists have hitherto had an oppor- 

 tunity of studying the amoebae of man, and few medical men have 

 possessed the zoological knowledge necessary for a proper investigation 

 of the material in their hands. What has already been published demon- 

 strates conclusively the need for further work on this subject by proto- 

 zoologists skilled in all the intricacies of their science ; and if I have 

 presumed to take so great a task upon myself, it is because no other 

 worker has yet volunteered for this difficult but urgent service. 



I have devoted a great part of my working life to the study of 



