1905.] NATURAL SCIENCES OF PHILADELPHIA. 551 



as long as the neviropodium. From the point of its appearance caii- 

 dally the notopodium and all other parts of the foot gradually increase 

 in size and become foliaceous, especially the neuropodial lobes and the 

 notopodial cirrus. At I.IX or LX the entire parapodium suddenly 

 becomes larger and more folicaeous, without, however, any change in 

 its fundamental characteristics. It is at this point that the posterior 

 genital region with its swimming setae begins. In a typical parapodium 

 of this region (fig. 46) both notopodium and neiu'opodium are large and 

 well separated. The former is the smaller and consists of a presetal 

 lobe broad at the base and with a nearly conical terminal portion and 

 a short, broad, presetal lobe situated somewhat ventrally. The cirrus 

 arises from the dorsal base and a little posterior to the notopodium, has 

 a relatively narrow but flattened base bent abruptly dorsad and bearing 

 a broadly orbicular style, the whole slightly exceeding the notopodium 

 in length. The neuropodium is comprised of the same parts as ante- 

 riorly, but the lo]:)es are very much broader and more foliaceous in 

 character; the two presetal ones are terminated by abruptly sjender 

 tips, while the postsetal lobe is both broader and blunt-pointed, as well 

 as shorter. The neuropodial cirrus is closely united with the base of 

 the neuropodium and tapers to an acute conical point reaching about 

 half way to the end of the neuropodium. The characters of the foot 

 become emphasized to at least LXXX, behind which the parts dimin- 

 ish gradually in size, the dorsal cirri alone remaining prominent to the 

 end but becoming narrower. Numerous large ova or aggregations of 

 spermatozoa are seen in parapodia of this region, but none anteriorly. 

 Both notopodium and neuropodiimi are each supported by a single 

 large tapering acicula. Setae are of two forms — compound in the neuro- 

 podium and simple in the notopodium. Both closely resemble those 

 of G. foliacea. The former are arranged in a vertical fan-shaped fascicle 

 and vary in number with the size of the neuropodium. They are color- 

 less, with usually strongly curved shafts terminated by oblique sockets, 

 and bear delicate, nearly straight or curved, acutely pointed and super- 

 ficially granulated ])lades. They increase in length both ways to the 

 middle of the fascicle and in the posterior region both shafts and blades 

 are greatly elongated, the exposed parts equalling h the width of the 

 body, while the longest in the anterior region are not more than ^ or A 

 the corresponding dimension. Simple setae appear with the notopodia 

 and, like the compound, are arranged in a vertically spreading fascicle 

 composed of never more than about 10 setae, of which 3 or 4 are ventral 

 to the acicula. They are colorless, shorter than the compound setae 

 and about twice as thick, slightly curved and rather abruptly tapered 



