Vlll PREFACE 



been prejudiced in this countr}- by the publication of Haeckel's 

 Plankton- Studien ! And how many people who have read that 

 brilliant but injudicial essay have seen Hensen's reply to it ! 

 I have tried critically to consider the weight of the various 

 objections that have been made against conclusions deduced from 

 the quantitative study of marine life, and trust that I have not 

 under-estimated these. Adverse criticism, which would surely have 

 been fatal to the development of an unsound method of investigation, 

 has certainly stimulated research on the lines suggested by Hensen. 

 Lohmann's work, for instance, was essentially critical and yet, more 

 than any other piece of plankton investigation published since 

 the appearance of Hensen's first memoir, it will facilitate the 

 quantitative study of the plankton. Admittedly imperfect and 

 incomplete as are these investigations, their results form never- 

 theless the most fascinating chapter of modern marine biological 

 research, and as such may be commended to the reader. 



I am indebted to my colleagues Miss M. Allen, and Mr H. J. 

 Buchanan- Wollaston for much kind assistance ; to Dr F. W. Gamble 

 for reading part of the manuscript ; and to Mr A. E. Shipley for 

 many suggestions, and much advice. 



J. J. 



Liverpool, 

 Jidy 1908. 



