Chsetopterus Variopedatus. 491 



with the internal lobes of the neiiropodia is indicated by uncinal 

 plates at its posterior margin alone. The external lobes are repre- 

 sented by small papillae on the margin of the palette. 



Posterior region. — The posterior region consists of the segments 

 between the sixteenth and the anus, which is on the dorsal side of 

 the terminal segment. The number, which varies considerably with 

 the age of the individuals, I have found from two, in a very young 

 specimen about one centimeter long, to fifty in an adult about thirty- 

 tw'O centimeters long when extended. Since the segments are iden- 

 tical in form, but in size they diminish progressively to the anus, 

 the description of a single segment (e. g., the nineteenth segment) 

 wall suffice for this whole region. The course of the intestine appears 

 as a greenish trail over the whole dorsal side. 



When the animal lies in its normal position in the tube the lateral 

 sides of the segment expose a pair of swaying conical notopodia whose 

 distal ends are directed vertically upward or obliquely outward from 

 the mid-dorsal line of the body. When filled with the sexual products 

 they are opaque, at other times transparent. Toward the anal seg- 

 ment, however, these notopodia are directed more and more laterally 

 till finally the last few pairs extend out horizontally and may be 

 directed posteriorly. Through the transparent integument of the 

 notopodia may be seen a bundle of straight slender setae of which no 

 portion extends to the exterior in fresh specimens. In mature males 

 during the breeding season the cavities of the notopodia are com- 

 pletely filled wdth sperm which gives this region a milky white 

 appearance (Fig. 4). The eggs, which float in the general cavity, 

 and the convoluted ovary give the sexual segments of the females 

 a roseate yellow tint. On the posterior (inferior) surface near the 

 base of each of the notopodia, i. e., between the notopodia of adjacent 

 segments, are located the nephridiopores. Each has the form of a 

 slight transverse slit in a small elevated area (Fig. 8). 



The ventral aspect of a segment is complicated through the presence 

 of a pair of median (internal) and a pair of lateral (external) lobes 

 of the neuropodia (Figs. 6 and 8). The internal lobe has the form 

 of a cylinder which is slightly flattened antero-posteriorly. It is 

 united along a portion of its mesial side with the adjacent lobe 



