APHRODITACEiE. 99 



ninth segments, and so on. This binary alternation of branchial 

 with abranchial feet is to be observed even in the species which have 

 no elytra (Palmyra) ; but it is not so constant as has hitherto been 

 believed, for in the genus Acoete branchial tubercles exist on all the 

 feet, their number being only fewer on the segments which carry the 

 elytra. 



In the families allied to AphroditacecRy there are species which 

 present no visible branchiae ; but when these organs exist, their form 

 or their position is essentially different. Thus in the Nereides they 

 affect the form of little fleshy, tongue-like processes, placed at the 

 end of the foot between the superior and inferior cirrus ; and although 

 in the Euniceacece and the Amphinomenacece they have nearly the 

 same position as in the Aphrciditacece, their configuration is very 

 dissimilar, being in the form of filaments more or less pectinated, 

 of tufts, of arbuscles, or of pinnatifid leaflets. 



In the majority of AphroditacecB the presence of elytra coincides 

 wdth the absence of superior cirri, that is, we find the latter only on 

 such feet as carry branchiae and do not bear scales. But this cha- 

 racter, like the preceding, is liable to exception, for in Sigalion there 

 is a superior cirrus to every segment of the body, whether elytrous or 

 not ; and this fact appears to invalidate the opinion of those who 

 maintain, with Blainville, that the cirri are the analogues of the 

 elytra, or modifications of the same organs, in those Annelides which 

 are not shielded with dorsal scales, — an opinion which, from the dis- 

 similarity of their position on the body, we might otherwise have 

 hesitated to adopt. The feet of the Aphroditacece are divided into 

 two branches, each furnished vdth a spine, with bristles, and with 

 cirri, whose figures vary according to the species. We have spoken 

 above of the superior cirri : the inferior are found on all the feet, 

 and offer nothing remarkable for notice, unless on the first segment, 

 where they are very large, and, with the superior, constitute ten- 

 tacular cirri, a sort of antennseform filaments placed at each side of 

 the head. But the true antennae, however similar in appearance, 

 are readily distinguished from them by their insertion on the head 

 itself: of these we generally reckon three*, a middle one and one 

 on each side ; and under and exterior to them there are two larger 

 setaceous filaments, which may without impropriety be denominated 

 palpi, since they are used to feel the way during the creature's pro- 

 gress. The eyes are black points on the upper surface of the head, 

 usually four in number, sometimes only two, and in Sigalion their 

 existence is doubtful. From the mouth a proboscis is at pleasure 

 evolved, which is armed with four jaws united in pairs, two above 

 and two below, opposed the one to the other by their cutting edge ; 

 and this disposition is one of the peculiarities of the family, for in 



* Savigny and Audouin and Milne-Edwards say five ; but if we limit, as I think 

 we ought, the term antennm to those filaments which are strictly cranial, there 

 are only three ; and what these celebrated naturahsts call external antennce, I 

 have, in the following descriptions, called palpi, since they originate under the 

 head, and are obviously different in structure, as they appear to be also in their 

 functions. See also Oersted, Consp. 5. 



H 2 



