422 F. W. GAMBLE AND J. H. ASHWOETH. 



highly organised than that of any other Polychgete at present 

 known, is sufficient to indicate that among other groups there 

 may he members which possess a highly sensitive organisa- 

 tion where we at present only suspect a slight power of 

 physiological response. The search for this important class 

 of evidence is at present a much more promising field than 

 the trodden paths of anatomy and embryology, though it is 

 clear that all these have to advance together in any attempt 

 to solve a phylogenetic problem. 



In this paper, however, we confine ourselves to the anatomy 

 and the post-larval developmental features of the family. 

 The work has been largely carried out in Manchester, but has 

 necessarily involved visits to the coast. We have examined 

 the Lancashire coast, the neighbourhood of Port Erin, Isle of 

 Man, Plymouth Sound, and St. Andrews Bay. To Professor 

 Agassiz we are specially indebted for the loan of specimens 

 of Arenicola from the Harvard Museum. We also wish to 

 express our thanks to M. Felix Mesnil for specimens of A. 

 Grubii and of Branchiomaldane from St. Martin, and to 

 Mr. J. E. Duerden, Curator of the Institute of Jamaica, for 

 obtaining, after much trouble, a specimen of A. cristata 

 from the shore at Bluefields. The Naples station has sent us 

 specimens of this species, Avhich is rare, or at any rate diffi- 

 cult to obtain in the Mediterranean, and also material repre- 

 senting A. Clap are dii and A. Grubii. For the post-larval 

 stages we are indebted to Mr. R. L. Ascroft and to Dr. 

 Benham, who gave us a specimen sent to him from Ply- 

 mouth. To Professor Hickson we owe several valuable sug- 

 gestions, and many of the facilities which have helped us in 

 the course of the work. 



The material upon which this paper is based has been col- 

 lected from many sources during the last three years. 



(1) Arenicola marina, Linn. — In addition to specimens 

 from various parts of the British and Irish coasts, and from 

 Jersey, we have received two specimens from the Harvard 

 Musevim, collected at Grand Manan, and also coloured draw- 

 JTig by Professor Agassiz of an undoubted example of this 



