ö PREFACE 



S. Parma (Amsterdam), F. S. Essapian (Miami, Florida), the late 

 Dr H. J. Slijper (Enschede), the late Prof. Dr R. Verheven (Brussels), 

 Th. Carels (The Hague), Dr C. de Hartog (lerseke), Capt. \\'. F. J. Mörzer 

 Bruins (Bussum), Mr and Mrs van Utrecht-Cock (Amsterdam), and 

 C. Naaktgeboren (Amsterdam), either for having suggested improvements 

 to the Dutch edition or else for ha\ing supplied new data and illustra- 

 tions. 



I am fully aware that despite so much help from eminent C[uartei-s a 

 book of this nature is bound to include a number of errors. I therefore 

 invite suggestion and criticism from any who feel qualified to give it. 



E.J. SLIJPER 



Zoölogisch Laboratorium 

 Plantage Doklaan 44 

 Amsterdayn C 

 The Netherlands 



