254 Annelida Chcetopoda 



for the basal three-fourths, becoming suddenly conical 

 externally. They gradually increase in length, and 

 become flattened, triangular, but the outer fourth or fifth 

 remains pointed, conical; on a few of the last segments 

 they again become shorter. 



The dorsal rami consist of a delicate linger-shaped 

 dorsal cirrus, shorter than the branchije. From a depres- 

 sion at the base of this cirrus a bundle of long simple setae 

 arises. Further back the dorsal cirri became as long as 

 the branchiae, and have nearly the same form. 



The ventral rami, on the first 25-29 segments, consist of 

 two transverse membranous lips, of which the anterior is 

 very low, hardly perceptible ; the posterior a well marked 

 plate, not reaching as far as the sette, and with a smooth 

 rounded margin. Between these lips are four rows of 

 stout blunt set«, straight or slightly curved (f. 123). 

 These setae are all short, first series shortest, increasing 

 progressively in length from first to fourth series. Between 

 the third and fourth series in the upper part of the ramus 

 are a few, usually two, long simple capillary setae (figs. 

 124, 125). The ventral rami are short on the first seg- 

 ment, increasing in length from the first to the sixth or 

 seventh segment. At this point they extend from the 

 dorsal to the ventral surface, never encroaching on the 

 ventral surface. The last seven or eight of this series of 

 rami decrease in length progressively, so that the last 

 (25th-29th) is about the same length as the first, and con- 

 tains about the same number of setae. The margin of the 

 posterior lip of the last three rami is prolonged into a 

 delicate cirrus. 



With the change of setae the anterior lip disappears ; the 

 posterior lip becomes conical, truncated, bearing a cirrus- 

 like prolongation on its lower outer border (f. 126), and 

 its position is changed to the lateral margin of the dorsum. 



