A POLYNOID WITH BRANCHIJ]. 445 



In spite^ however, of their being so unlike respiratory organs 

 in structure, their outward resemblance to the "branchiae" of 

 other Polychaetes, and especially to those of the Amphinomidse, 

 struck me so forcibly that I was led also to examine micro- 

 scopically the structure of these for the sake of comparison ; 

 and the results are, I believe, sufficiently interesting to warrant 

 a mention of them here, although I must defer a more detailed 

 description and more numerous figures to a future publica- 

 tion. 



I have examined by means of sections the branchiae of a 

 Euphrosyne, of two or three Amphinomes, of Chloeia flava, 

 of Eunice gigantea, Diopatra neapolitana, Arenicola 

 marina, and a few others. The thickness of the cuticle, 

 although most marked in the Amphinomids, is remarkable in 

 all. In none of them nor on any part of them is the epidermis 

 ciliated. Very minute concretions, nothing like so large as in 

 Eupolyodontes Cornishii, are present in the branchiae 

 of the Euphrosyne, one of the Amphinomes, in Areni- 

 cola marina, and, although here they are present in other 

 parts of the epidermis as well, in Eunice gigantea. Cla- 

 parede (4, p. 110) has already remarked on the thickness 

 of the cuticle, and the absence of blood-vessels and of axial 

 cavity in the branchiae of Euphrosyne Audouini, and 

 speaks of them throughout as " pretendues branchies.^' 

 Schmarda shows, however, that in E. polybranchia there 

 is a vascular network penetrating into the final ramifications, 

 and in the Euphrosyne of which I cut sections, and which I 

 believe to be E. borealis, there were certainly two vessels 

 traversing the main stem of each branchia, breaking up into a 

 capillary network in the filaments. We have, then, within 

 the same genus forms with vascular and with non-vascular 

 " branchiae." In most of the Amphinomes of whose branchiae 

 I cut sections the filaments appeared also to be solid. There 

 was, however, in one of them at least (fig. 12) a central part 

 very little blocked up by connective tissue. Between this and 

 the epidermis is retiform connective tissue {c. t.), and in this on 

 either side of each filament is a blood-vessel {bl.), giving off 



