viii PREFACE 



will be found under their respective headings. My own experience is that 

 in reading elaborate monographs the multiplicity of details tends to throw 

 one off the main course of the argument. Details of minor importance are 

 much better referred to their proper place instead of being included in one 

 long dissertation on the structure of the group. I have therefore attempted 

 to give in my introductory chapter such an account of the anatomy of the 

 Oligochaeta as may be sufficient to satisfy any person not interested in the 

 minute details, but desirous of having the main facts stated in as few words 

 as possible. It may be thought that I have erred in the brevity of this 

 chapter : I claim, however, to have put before the reader a more complete 

 account of the structure of the group than can be found in any treatise yet 

 published, and I have done my best to avoid details not of special significance 

 except as generic or specific characters. 



In the systematic part I have not treated each family in a precisely 

 similar fashion. In the Perichaetidae, for example, the internal structure is 

 dealt with after the definition of the family ; in the Geoscolicidae, anatomical 

 details are reserved as generic characters. In the highly peculiar group 

 Eudrilidae the method adopted is somewhat intermediate. In each case the 

 plan followed is not, as might perhaps be suspected, the result of the dis- 

 continuous preparation of this monograph, but has been deliberately selected 

 as being, in my opinion, most appropriate to the family in question. 



For material used in the preparation of this work I am greatly indebted 

 to Dr. Benham, Prof. Claus, Mr. W. T. Thiselton-Dyer, C.M.G., F.R.S., 

 Mr. Chamberlain, Mr. Gustav Eisen, Mr. Everett, Mr. F. Finn, Dr. Gregory, 

 Prof. Loven, Dr. Michaelsen, Prof. M'Intosh, F.R.S., Mr. Alvan Millson, 

 Prof. T. J. Parker, F.R.S., Prof. Poulton, F.R.S., Dr. D. Sharp, F.R.S., 

 Mr. W. W. Smith, Mr. Sowerby, Prof. Baldwin Spencer, Prof. Vejdovsky, 

 the Rev. H. W. Woodward, the St. Petersburg Museum, and the Zoological 

 Society of London. 



FRANK E. BEDDARD. 



LONDON, February, 1895. 



