PREFACE. Vll 



afraid that this charge is true. I can only hope that my 

 carelessness in this respect will not cause my readers serious 

 annoyance. 



To make the book more complete as a work of reference, 

 I have endeavoured to mention and give an account of as 

 many families as possible. For the same reason I have 

 named a large number of genera without giving any account 

 of them. It may appear to some absurd to name without 

 describing so many genera. My object in doing it has 

 been to make the book more useful in enabling students to 

 track as many unknown names as possible to their place 

 in the system. 



I must ask the indulgence of my readers towards the 

 many imperfections of this work. It is impossible to have 

 a specialist's knowledge of every group, and in a book of 

 this size, dealing with an enormous number of facts and 

 names, it is beyond human capacity to avoid mistakes. Every 

 care has been taken, and it is hoped that they will be found 

 to be neither numerous nor important. The errors would 

 undoubtedly have been much more numerous had it not 

 been for the kind assistance given me by my friends. To 

 Mr. J. J. Lister I am especially indebted. He has looked 

 through all the proof sheets, and has brought to bear a 

 critical power and discrimination which have been invalu- 

 able. I cannot be sufficiently grateful for his assistance. 

 Mr. Lister has also contributed the account of Coral Eeefs, 

 and of the reproduction of the Foraminifera. My thanks 

 are also owing to Mr. Heape and Mr. Graham Kerr. who 

 looked through the greater part of the proofs, and to Mr. 

 Shipley, Dr. Benham, Professor Haddon, and Dr. Harmer, 

 who looked over the proofs of portions of the book, and 

 gave me the benefit of their special knowledge. I have 

 thus often been saved from errors into which I should other- 

 wise have fallen. My principal sources of information are 

 acknowledged in the foot-notes ; but I must not omit to make 

 mention here of works from which I have obtained special 

 help ; these are Biitschli's Protozoa in Bronn's Thierreich, 

 Chun's introductory account of the Coelenterata also in Bronn, 



