PEEFACE. 



oJ<Ko 



It was originally intended that the two volumes of the ' Eotifera ' 

 should contain all the foreign, as well as all the British species ; 

 but, while the work was being written, so many new British forms 

 were discovered, that want of space compelled the authors to omit 

 all but a few of the more remarkable foreign Eotifera. The 

 Supplement, however, now remedies this omission ; and completes 

 the work, by describing every known foi-eign species, as well as 

 the British that have been discovered since its publication in 1886. 



Upwards of one hundred and fifty species ^ have been added, in 

 the Supplement, to the two hundred and fifty already described in 

 vols. i. and ii. ; and, in ahnost every case, the description is ac- 

 companied by a figure. Besides these, more than forty doubtful, 

 or imperfectly described species, have been briefly discussed, and 

 occasionally illustrated. Both the descriptions and drawings of the 

 foi-eign species have been taken from the original memoirs in which 

 they first appeared ; the doubtful, or insufficiently described species, 

 as well as the mere sjmonjmis, being distinguished from the others 

 by their position in each genus, and by the arrangement of the 

 type. 



The Bibliographj' has been considerably enlarged, and now 

 exceeds two hundred memoirs, the greater part of which I have 

 studied : all of them directly refer to the subject, and most of them 

 are weU worth the reading. 



It is hardly necessary to add, that the labour of condensing 

 such a mass of materials into a short Supplement has been great ; 

 especialh' when conflicting statements had to be weighed, and there 

 was no opportunity of checking them by observations on the 

 animals themselves ; but I was anxious to complete the work, and 



' Sixty of these are new British sijecfes discovered by Mr. Gosse. 



