MR. Tj. C. BOUSFIELB ON THE GENUS DERO. 



91 



The Natural History of the Grenus Dero. By Edward C. Bous- 

 riELD, L.R.C.P. Loud. (Communicated by Dr. J. Murie, 



r.L.s.) 



[Eead 4th November, 1886.] 

 (Plates III.-Y.) 



At the meeting of the Britisli Association in 1885, at the request 

 of Prof. Mcintosh, I presented a summary of the results of 

 my study of the Annelids of the genus Dero, with descriptions 

 of some new species which had come under my notice, and 

 remarks as to the identification of others. From the necessary 

 limits of such a commuuication, I was compelled to omit 

 much detail ; and lack of time and material led to a certain 

 want of accuracy in my collation of the work of other writers, 

 and the comparison of the examples which came under my own 

 notice with their descriptions. 



Enlarged facilities of reference having now enabled me to 

 acquire a tolerably complete knowledge of all that has hitherto 

 been written on this genus, and a considerable supply of material 

 from various sources having given opportunities for extended ob- 

 servation and closer comparison, I venture to offer the following 

 as the most complete account of the genus allowed by the present 

 state of knowledge. Four uew species having been met with in 

 the course of the eighteen months or more during which I have 

 been working at these Annelids, it would appear probable that 

 others still remain to be discovered ; and it is to be hoped that 

 the publication of a summary of what has at present been accom- 

 plished may facilitate future observation. 



History and JBihliograpJiy. 

 The Annelids with which this paper deals, though their biblio- 

 graphy covers a period of a century and a quarter, have hitherto 

 been the subject of very little original work, owing probably to 

 their habits of life, which prevent their presence in a state of 

 nature from being easily discovered. In view of the great advances 

 which have been made in methods of research, and especially in 

 optical appliances, the very evident way in which the observations 

 of earlier writers, and their interpretations (not unfrequently 

 erroneous), have been copied by later authors, in many cases 

 almost verbatim et literatim^ is not a little surprising. 



