A POLYNOID WITH BRANCHI^. 447 



their structure is very diflFerent^ as will be seen by comparing 

 the figures of two sections through one of them (figs. 11a and b) 

 with fig, 7. There is apparently no central cavity, nor is there 

 anything looking at all like blood-vessel ; the epidermis cells 

 are flattened and contain no concretions : the only point of 

 resemblance is the thickness of the cuticle. The substance of 

 the filament near the tip seems to consist of concentrically 

 arranged connective-tissue fibres, in which lie a few large 

 clear cells with large distinct nuclei. Five of these (fig. 11a) 

 are arranged radially round a common centre, and their 

 appearanceis extremely suggestive of the so-called "gill-glands" 

 recently described in a Crustacean by Mr. Allen (1) (where, 

 by the way, we have also an instance as shown by Kowalewsky 

 of a branchia exercising some excretory function besides its 

 normal function). It is true there is nothing to be seen here 

 representing the duct described by him ; but one could perhaps 

 scarcely expect to find it, even if present, in material not pre- 

 served with a view to histological work, and also the plane of 

 the sections might not be favorable for showing it. Nearer 

 the base of the filament (fig. 11a) the whole space beneath the 

 epidermis seems to be occupied by retiform connective tissue, 

 except for a curious mass of what seem to be concentrically 

 arranged connective-tissue fibres near the centre. The struc- 

 ture of these filaments bears most resemblance to that of 

 the branchiae of Euphrosyne — in as far as I have been able to 

 examine them — amongst Polycheetes. Here also, in the "E. 

 borealis (?) " at least, we have similar large cells embedded 

 in connective tissue near the apex of the filament, although 

 not radially arranged round a common centre as in the 

 Eupompe filament, and the large cells in a special swell- 

 ing at the apex of the branchial filaments of so many Euphro- 

 synes (including E. Audouini) are well known, although 

 I do not know that sections of them have ever been described. 

 The rest of the substance of the branchial filament is occupied 

 by connective tissue, in which, however, in E. borealis (?) 

 there are wall-less blood-vessels, though apparently there are 

 not even these in E. Audouini. 



VOL. 35, part 3. NEW SEE. H H 



