xii Intj-odnction 



Collections of Arenicola in the Museums of Berlin, Paris, Cambridge 

 (Mass.) and the Smithsonian Institution, together with interesting 

 examples from the Museums of Copenhagen, Dublin, Hamburg, 

 Eeykjavik, St. Petersburg, Stockholm and Vienna, have been sent to 

 me for examination. I am much indebted to the authorities of these 

 institutions for placing their material at my disposal. During the 

 last twelve years I have collected, and many friends have generously 

 sent to me, large numbers of specimens of Arenicola, in various stages 

 of growth, selected examples of which have recently been added to 

 the British Museum Collection, The possession of this abundant 

 material has enabled me to revise and extend previous work upon 

 the characters used in diagnosis, and to ascertain their range of 

 variation. In addition to the acknowledgments made in the text, I 

 am glad to have this opportunity of tendering my sincere thanks to 

 the following friends, who have aided my work by the gift or loan of 

 specimens : Prof. W. B. Benham, P.E.S., Prof. H. C. Bumpus, 

 Geheimrat Prof Dr. E. Ehlers, Prof P. Pauvel, Prof. J. D. F. 

 Gilchrist, Prof. W. A. Haswell, F.Pt.S., Prof. Harold Heath, Prof. 

 A. D. Howard, Dr. E. S. Lillie, Prof. F. Mesnil, Mr. E. Southern, 

 and the Directors of the Marine Laboratories at Alexandrowsk (Gouv. 

 Archangelsk), Cette, Millport, Plymouth, Sautander, Sevastopol and 

 Trieste. 



To Prof. F. Jeffrey Bell and to Dr. James Eitchie, of the Eoyal 

 Scottish Museum, Edinburgh, who have kindly read the proofs, I am 

 greatly indebted for helpful suggestions. 



J. H. ASHWOiriH. 



Zoological DErARTMENT, 



University of Edinburgh. 



Sepfemhcr 23, 1912. 



