272 THE ANNELIDA POLYCHAETA. 



first parapodia, the notocirrus, attached proximad of the middle, is tapered from 

 the base distad, flattened, and long, extending forward well beyond the bases 

 of the posterior ceratophores ; the nem-ocirrus is attached at the base of the 

 parapodium on the ventral side and is similar in form to the notocirri, but shorter; 

 in front of the series of setae there is a distinct but short, flap-like, distally convex, 

 presetal lobe, this being much exceeded by the setae, while behind the setae 

 there is a very long cirriform process, about equal in actual length to the neuro- 

 cirrus. In succeeding parapodia the presetal lobe soon quite disappears as 

 such. The postsetal process caudad gradually decreases in length, the distal 

 portion soon being represented only as a short, pointed process from a broad 

 basal flap like the presetal lobe farther forward; and in this form of a thin lobe 

 bearing a short pointed piece distally, the postsetal processes continue to the 

 end of the fragment with no essential further change. The notocirrus is present 

 on all parapodia of the body; but caudad it rapidly becomes reduced and on 

 all but the more anterior segments appears as a slender filament of uniform 

 diameter, or nearly so, throughout its length. The neurocirrus continues as a 

 long and conspicuous, tapering process to the seventh parapodia, except that the 

 right seventh cirrus is much reduced in contrast with the left one, which is large; 

 on the eighth parapodia the neurocirrus is reduced to a slight elevation and 

 thereafter appears merely as merged in a scale in the ventral glandular area. 



The branchiae begin on the fifth parapodia, each being a single slender, 

 distally pointed filament arising from the base of the notocirri, and about equal- 

 ling the latter in length. On the sixth parapodia the branchiae are similar. 

 On the seventh, each branchia is bifurcate, the two filaments arising symmetri- 

 cally from the base; on the right side one filament clearly exceeds the notocirri, 

 but on the other side there is but little difference. On the eighth and ninth 

 parapodia each branchia is similarly bifurcate, with the filaments but slightly 

 exceeding the notocirrus. The tenth to fourteenth parapodia, inclusive, bear 

 each a trifilamentous branchia, the inner two separating from each other higher 

 up than the primary bifurcation. The next two branchiae have four branches. 

 Following there are branchiae with five filaments and then with six, rarely more, 

 eight being the maximum number observed. (Plate 44, fig. 4, 5). The fila- 

 ments in them arise in an essentially unilaterally pectinate manner, the filaments 

 being at a very acute angle with the stem; they attain or sometimes a little 

 surpass the middorsal line, thus very much exceeding the notocirri. Branchiae 

 continue to the end of the fragment (CXIX somite), in the posterior portion of 

 which the number of filaments is again four, the number that prevails. 



