446 FLOEKNOE BUCHANAN. 



numerous branches all lying in the connective tissue. Only 

 quite at the extremity of the filaments the connective tissue 

 and vessels seem to have disappeared altogether. In Chloeia 

 (fig. 13) the two vessels have increased enormously in size, and, 

 except for being connected with one another at intervals at the 

 tip of each filament, give off no branches. No central cavity 

 is distinguishable, all the space which is not blood-vessel under- 

 neath the epidermis being occupied by retiform connective 

 tissue (c. t.). In the other Polychsetes examined the branchiae 

 were more normal in structure, containing an afferent and 

 efferent vessel lying close under the epidermis, but in a well- 

 developed extension of coelom.^ 



From the above facts I conclude that the so-called " bran- 

 chiae" of polychsetes do not necessarily serve only as respiratory 

 organs, and indeed may even have no respiratory function at 

 all (some species of Euphrosyne) ; and in the sense that we call 

 them " branchise,^' on account of their representing the respi- 

 ratory organs of allied forms, I claim to be able to apply the 

 same term to the branching processes on the parapodia of 

 Eupolyodontes Cornishii. When they are not respiratory, 

 or at least not mainly respiratory in function, they may have to 

 do with excretion, serving to store the excretory products, and 

 probably, in the case of Amphinome at least, and those forms 

 with blood-vessels immediately underlying the epidermis and 

 with concretions in the epidermis cells, to form them from 

 the blood. 



In conclusion, I should like to draw attention to the minute 

 structure of the filaments on the parapodia of the only other 

 Acoetid possessing them which I have been able to examine, 

 namely, Polyodontes(Eupompe)australiensis. Although 

 I think there can be no doubt, from their position in relation 

 to the parapodium, as to their representing the more numerous 

 filaments on the parapodium of Eupolyodontes Cornishii, 



^ Ouly in the Diopatra it was difficult to be certain of the blood-vessels, as 

 the blood did not clot at all, and the two vessels in each of the filaments, each 

 of them subdivided by connective-tissue partitions, would not be taken for 

 blood-vessels, were it not for Claparede's statement that there is an afferent 

 and efferent vessel in each filament. 



