Chsetopterus Variopedatus. 489 



Laffuie is probably correct in giving the homology of this acces- 

 sory feeding organ as follows : "The dorsal sucker (cupping-glass) 

 formed by the tenninal portions of the two dorsal rami united in the 

 median line, is rounded externally and hollowed out internally into a 

 deep cavity. Longitudinal and transverse sections clearly show its 

 structure. The wall is double and the space comprised between the 

 two walls is a diverticulum of the general cavity." My observations, 

 which are based on dissection and sections, verify his observations that 

 the wall is double and that the space between the walls is a diverticu- 

 lum of the general cavity. Numerous muscle strands join the inner 

 and outer walls of the pouch to one another. In regard to the func- 

 tion of this accessory feeding organ Laffuie says (page 264) : "This 

 dorsal cupule functions as a true sucker and enables the animal to 

 adhere to the inner wall of its tube. This is easily verified by care- 

 fully removing a few Chsetopteri from their tubes. This sucker is 

 the only part situated upon the dorsal surface which could be used for 

 holding the animal in its tube." I never once, among more than two 

 hundred specimens, observed the structure in use as an attaching 

 organ, but I have frequently observed that in some individuals it 

 contained a greenish mass of diatoms and other organic matter 

 mingled with mucus. The presence of nutritive material in this 

 pouch led me to search first for a direct communication with the 

 intestine at this point in order to acount for the presence of this mass 

 of food so far removed from the mouth. The introduction of finely 

 divided particles of carmine in sea water into the pouch at once 

 demonstrated a strong ciliary current running directly or obliquely 

 from the margin to the deeper portion of the pouch. Here the parti- 

 cles were rotated for some time, but they were later discharged from 

 the pouch in a manner that will be taken up in the next chapter. 



Fourteenth, Fifteenth and Sixteenth Segments. — The fourteenth, 

 fifteenth and sixteenth segments together are somewhat shorter than 

 the anterior region, but when the animal is extended they occupy 

 nearly half of the middle region of the body. They form a series 

 of very muscular campanulate organs, each with its base directed 

 forsvard. One side lies against the ventral longitudinal muscles 

 from which tlicv derive the muscle strands that make them effective 



