FROM THE MERGUI ARCHIPELAGO. 



263 



The branchial filaments are furnished at their tips with well- 

 developed eyes, a single eye to each branchial filament. 



In the relation of these eyes to the extremity of the branchial 

 filament, the present species is particularly like Brancliiomma 

 vigilans *; that is to say, that the terminal region of the branchial 

 filament is prolonged for a considerable distance beyond the eye, 

 which is attached to its under surface. 



The eye of B. intermedium, however, appears to differ a little 

 in shape from the last-named species as well as from the others ; 

 it is somewhat mushroom-shaped (PI. XXI. fig. 6) ; the stalk of 

 attachment to the branchial filament is pigmented. 



An interesting point about the branchiae o£ this species is illus- 

 trated in the same figure ; towards the extremity is a double fold 

 just overlying the eye ; the two halves o£ this fold appear to 

 coalesce (figs. 6 and 7) posteriorly, and gradually to die away 

 towards the base of the branchial filament. It seems to me per- 

 missible to compare this structure to the dorsal filaments on the 

 branchiae of Dasychone, and on that account I have named this 

 species "intermedium" This character does not seem to occur 

 in other species — it has not, at any rate, been figured or referred 

 to — and therefore will serve to distinguish the present species. 



Another species which, coming from the same quarter of the 

 globe, will be confounded with this, is Sabella acropJithalmos of 

 Grubef- Grrube, however, says nothing about the dorsal laminae 

 upon the branchial filaments, and compares the species generally 

 with Brancliiomma vesiculosum. I apprehend, therefore, that 

 the relation of the eyes to the gill-filaments is more like that of 

 B. vesiculosum than B. vigilans. 



There are two tentacles about one third of the length of the 

 branchial filaments ; each tentacle is slightly curved, and tapers 

 gradually towards its free extremity, which bears a certain 

 amount of pigment on the inner side ; the inner (curved) edge of 

 the tentacle bears a number of extremely delicate hair-like 

 filaments. 



Dasychone serratibranchis, Grule. 



Dasychone serratibranchis, Grube, Beitrage fur Annelidenfauna etc. 

 p. 262. 



The collection contains several specimens of a Dasyclione which 

 I refer to this species. 



* Loc. ext. p. 501. t Loc. ext. p. 258. 



LINN". JOURN. — ZOOLOGY, VOL. XXI. 



22 



