PREFACE 



rriHERE are already two works dealing with the Order Oligochaeta. The 

 -*- first of these, in time of publication, is Professor Franz Vejdovsky's 

 'System und Morphologie der Oligochaeten,' which appeared in 1884. Six 

 years later Professor L^on Vaillant contributed to the volumes on the 

 Annelids of the ■ ' Suites h, Buffon ' a volume and a half dealing with the 

 same group. It might appear, therefore, at first sight, that the ground has 

 already been taken up, and that there is no occasion for the present work. 

 Tt must be recollected, however, that it is nearly ten years since the 

 publication of Professor Vejdovsky's treatise, and that during this period 

 our knowledge of the Oligochaeta, more particularly of the earthworms, 

 has increased enormously. Professor Vejdovsky's object, moreover, was more 

 especially to give an account of the structure of the group from his own 

 observations, and to spend less time in dealing with the results of other 

 observers — not that the previous work upon the group was by any means 

 neglected by him, but no great amount of detail was given as to the 

 genera and species of Oligochaeta not occurring in his native country. 



M. Vaillant's work is rather more comprehensive in scope, but there 

 is no account of any researches made after the year 1 886 ; so that the large 

 amount of literature which has appeared since that date has not yet been 

 incorporated into any general work. M. Vaillant's contribution also is rather 

 more devoted to the systematic side of the subject than to the description 

 of structure. 



Under these circumstances it appeared to me that there was room for 

 a treatise of rather wider scope than those of either Professor Vejdovsky or 



