A POLYNOID WITH BRANCHLE. 437 



the other species although extremely reduced. Their relation 

 to the eye-stalks suggests for a moment their homology with 

 the paired prostomial tentacles {" antennae " of authors) rather 

 than with the palps, but if this were the case we should have 

 not only to regard the palps as altogether absent, but we 

 should also have to explain the presence of an extra pair of 

 prostomial tentacles in front with no homology in other forms. 

 A comparison of the arrangement of the diflferent prostomial 

 appendages 1 in the sessile-eyed forms shows that there also, 

 as in P. gulo and the new worm, the paired prostomial ten- 

 tacles arise close to the anterior edge of the prostomium, while 

 the only other paired prostomial appendages, the palps, arise 

 close behind them and are developed to their usual extent.^ I 

 think, therefore, that we may conclude that the relation of any 

 of the prostomial appendages to the eye-stalks is a secondary 

 one, while their relation to the prostomium is constant.^ The 

 parapodia of P. gulo are not figured, but from the description 

 they seem to resemble in arrangement those of the new 

 species. 



The only characteristic points of difference between P. gulo 

 and the new worm is that while in P. gulo there is no trace of 

 a median prostomial tentacle here there is one, although only 

 a very rudimentary one ; and that the few dorsal papillae on the 

 parapodia of P. gulo, some of which are described as elon- 

 gated to cirri, are here enormously developed and very numer- 

 ous and arborescent, resembling in appearance the branchiae 

 of other Polychsetes. Both these points, however, seem to me 

 to be only of specific importance, since they are characters 

 which vary also in other members of the group. While the 

 other characters of the prostomium, so much alike in these 

 two species, but differing so markedly from all the other forms, 

 seem to mark them off from all the others as a separate genus, 

 for which I propose the name Eupolyodontes, calling the 



* " Prostomial appendages " = 1 median and 2 paired " prostomial ten- 

 tacles" + 2 "palps." 



^ Compare Ehler's figure of head of Euarche tubifex (7). 



' Not wishing to spoil the specimen I was unable to examine microscopi- 

 cally the structure of the diiferent pairs of prostomial appendages. 



