A POLYNOID WITH BRANOHI^. 443 



would be exceedingly interesting, as it would suggest that 

 other sessile-eyed forms might be but second forms of other 

 species with pedunculate eyes ; but I think evidence is wanting 

 of the fact that the two specimens described by Grube as P. 

 bicolor do really belong to the same species. Unfortunately 

 neither of them is figured at all. Panthalis nigromaculata, 

 which I have also placed with a (?) in this genus, would appear 

 from Grube's figure of its head to have quite sessile eyes. In his 

 description of it, however, he speaks of them as on protuberances. 

 Besides throwing light on the intrinsic relationships of the 

 sub-family, the new worm also, it seems to me, increases the 

 probability of the existence of a relationship between the 

 whole family of the Polynoidse and the family Amphinomidae. 

 The Acoetidae, in common with certain other sub-families of the 

 Polynoidse, resemble the Amphinomidse in the forward move- 

 ment of the first pair of parapodia. The new Acoetid re- 

 sembles them further in another peculiarity of the head which 

 I have already mentioned, namely, the ridging of the dorsal 

 surface of the head behind the median tentacle. The resem- 

 blance may be only superficial, but one is certainly reminded 

 by it at once of the ^' caruncle " of the Amphiuomidse, which 

 is sometimes little more than a raised part of the dorsal sur- 

 face of the head. Another and more striking point of resem- 

 blance, at first sight at least, is the presence of the arborescent 

 or filamentous, branchia-like looking structures on the para- 

 podia, and this brings me to what I consider the most in- 

 teresting point about the new worm. I have already men- 

 tioned the position of these filaments and referred briefly to 

 their structure in diagnosing the species. Their relation to 

 the parapodiura is shown in figs. 4 and 5, a single tuft of 

 them in fig. 6, and a transverse section of one of them in 

 fig. 7. The state of preservation they were in makes their 

 minute structure difficult to interpret, and I cannot be at all 

 certain whether the central cavity is really an extension of 

 coelom or a large blood-vessel, — that is to say, whether there 

 is a true space between the epidermis and wall of this central 

 cavity or not. I am inclined to think that there is no cavity 



