

BRITISH GEPHYREA 449 



Sipunculus, but since these open neither into the body-cavity nor 

 into the alimentary canal, it is hardly fair to compare them. 



The resemblances between the Orders seem to me, on the 

 whole, to outweigh the differences. The general structure of 

 the skin, the coiled alimentary canal, with its ciliated groove, 

 supported by strands of muscles, the vascular system which 

 gives off no capillaries, the structure of the brown tubes, the 

 existence of chitinous hooks or bristles, the nervous system with 

 its single unsegmented ventral cord, the formation of the generative 

 organs, all point to a sufficiently close resemblance to justify us 

 in classing the two Orders together. In addition to these 

 there are considerable histological resemblances which cannot 

 be discussed here, but which have a certain weight. 



To sum up, it seems probable that the Echiuroidea are derived 

 from the Chaetopoda, and that their nearest ally in this group 

 is Sternaspis ; and that the Sipunculoidea are allied to the Echiu- 

 roidea, but have further departed from the Annelid stock, and have 

 lost even those traces of affinity with the parent group which have 

 been preserved in the development of Echiurus and Thalassemia. 



So little is known of Epithetosoma that it is difficult to 

 discuss its affinities. The presence of the hollow proboscis and 

 the pores leading into the body- cavity undoubtedly justify its 

 being placed in a separate Order, but beyond the presence of a 

 terminal anus, in which it resembles the Echiuroidea, there is 

 nothing in its structure which connects it more nearly with one 

 than with the other of the three larger Orders of Gephyrea. 



List of Gephyrea found in the British Area as defined by 

 Canon Norman. 



Phascolosoma vulgare Blainv. English Channel and North Sea. 



,, elongatum Kef. English Channel. 



papillosum Thorn. English coast. 



eremita Sars . North Sea. 



procerum Moeb. Bass Rock. 



Phascolion strombi Mont. . English coast (Plymouth). 



Sipunculus nudus L. . . North Sea, English Channel (Paignton, Teign- 



mouth). 



Golfingia macintoshii Lank. . East coast of Scotland (St. Andrews Bay). 



Petalostoma minutum Kef. . English Channel (Plymouth). 



Priapulus caudatus Lam. . Scarborough, Outer Hebrides. 



Echiurus pallasii Guerin . Coast of Scotland, English Channel. 



Tlialassema neptuni Gaertner . English Channel (Coast of Devonshire). 

 VOL. II 2 G 



