xii PREFACE. 



Dr. Albert Giinther, and the late Dr. Baird of the British Museum, Mr. G. S. Brady of Sunderland, 

 Dr. Carrington of Eccles, Mr. J. F. Whiteaves of the Natural History Society, Montreal, and 

 Prof. Dickie, Aberdeen, have also aided him by the communication of preserved examples or 

 otherwise. Mr. Gwyn Jeffreys included some in his rich collections of Zetlandic Annelids, and, 

 in conjunction with Dr. Carpenter and Prof. Wyville Thomson in the celebrated " Porcupine-" 

 Expeditions of 1869 and 1870, he secured a most valuable collection of Annelids and Nemerteans, 

 which was most courteously placed at the author's disposal by these gentlemen. To all these he 

 begs to return his sincere thanks for their valued assistance, and specially to Dr. A. Giinther, for 

 his exertions in 1869. He has also to remember the many valuable hints in the microscopic 

 department of this work received from the experienced hands of the late Dr. Eraser Thomson of 

 Perth. Nor must he omit to acknowledge the steady encouragement given throughout these 

 researches by Prof. G. Busk, whose cordial support at an early period was a source of the greatest 

 satisfaction. 



He has further to thank Professors De Quatrefages of Paris, E. Grube of Breslau, Kolliker 

 of Wurzburg, and Van Beneden of Louvain, Mr. Alex. Agassiz of America, and Dr. Malmgren 

 of Helsingfors, for their esteemed aid, by the communication of papers and otherwise. Two 

 others, unfortunately, have since been early lost to science, viz. Professors W. Keferstein of 

 Gottingen and E. Claparede of Geneva. The former did much to place Nemertean anatomy on 

 a proper basis, and his conscientious original investigations gave promise of great advances in this 

 as well as in other departments. M. Claparede, again, was, perhaps, the most distinguished 

 investigator of the Invertebrates, especially the Annelida, of his time, and his splendid work 

 both with pen and pencil will make his name enduring. 



To the list of these losses he has now to add the lamented Dr. Baird, whose excellent labours 

 amongst the collection of Annelida in the British Museum will long be remembered, no less 

 than his genial and kindly aid to all interested in zoology. 



For the delay in the issue of this portion of the work — a delay originating in the printing 

 of the Plates — the author is not responsible, since it was ready at the end of 1869. He has to 

 thank the Council of the Bay Society for their liberality in regard to the Plates, and Mr. Ford for 

 his masterly touch in their execution. 



Murthly; September, 1873. 



