POLYXOE SQUAMATA. 203 



ridges, like those of the short setae, but toward the middle 

 (F) these ridges appear to encircle the blade completely, as- 

 suming the aspect of so many closely -imbricated concentric 

 scales, before finally becoming obsolete upon the extremity 

 of the seta. 



The neuropoclial aciculum needs no special notice, except 

 that the extremity of its trichophore projects as a sort of 

 papilla, less obvious in full-grown specimens, which divides 

 the neuropodium into an upper and a lower portion, the for- 

 mer containing about half as many setae as the latter. The 

 apertures of the trichophores are placed between lobe-like 

 prolongations of the neuropodium, to which the special term 

 of labia (Grube) may be applied. In this species they pre- 

 sent no remarkable peculiarity beyond their inequality. 



The neuropodial setae (Fig. 52, C, Z*), although at first 

 sight very different from the notopodial setae, are, in truth, 

 constructed on essentially the same plan, the blade being 

 short, while the handle is proportionally elongated. The 

 blade is subcylindrical at its base, pointed and slightly curved. 

 Eight or nine transverse ridges extend around about two-thirds 

 of the circumference of its proximal half ; the basal ridges 

 are narrow, and merely serrated, but toward the apex the 

 ridges become deeper, and the serrations pass into strong 

 teeth ; at the same time, one side of the ridge is elongated 

 into a strong point. 



Attached to the under surface of the parapodium by a 

 somewhat enlarged base, with which it is articulated, is a 

 smooth, conical, very flexible filament — the neuropodial cir- 

 rus (Fig. 51, c') ; it hardly reaches to the end of the neuro- 

 podium. Again, springing from the neural surface of the 

 somite, close to the parapodium, there is a small pyriform 

 tubercle (A), divided by longitudinal grooves into about eight 

 segments. This is possibly connected with the reproductive 

 function. 



The appendage of the notopodium, or rather of the noto- 

 podial side of the parapodium and somite, varies according 

 to the particular somite which may be examined. In some 

 somites this appendage is a cirrus (Fig. 51, D, c) similar to 

 the neuropodial cirrus, but much larger, equaling the semi- 

 diameter of the body in length, and presenting an enlarged 

 pigmented bulb of attachment to which the filament of the 

 cirrus, which is cylindrical for about two-thirds of its length, 

 and then becomes enlarged and suddenly tapers to its extrem- 

 ity, is articulated. 



