INTESTINAL RESPIRATION IN ANNELIDS. 809 



Antiperistaltic contractions of the intestine seem to be absent. In one case they 

 were observed in the posterior portion of the stomach. 



Specimens of Histriohdella Jiomari yielded negative results. Slight ciliary move- 

 ment was observed in the last part of the intestine, but it was directed towards the 

 anus, which was kept closed. Irregular contractions of the intestine occurred, but not 

 definitely in either direction. 



It may be added that the intake of water by the anus is a recognised occurrence in 

 Polygordius ; and that Goodrich has observed ascending ciliary action in Nerilla (22). 



Nemertinea. 



While engaged at Millport in working at the Nemertines of the Clyde, I took the 

 opportunity of examining all the species I came across (in most cases numerous 

 examples), in order to determine whether or not similar phenomena occurred in that 

 group. The results were mostly negative ; the anus is a very small orifice, and is 

 usually invisible even by the microscope ; it is never held open, and consequently there 

 is no possibility of the entrance of water for respiratory purposes. Ciliary movement 

 was never visible within the alimentary canal. A few infrequent antiperistaltic waves 

 were seen to pass along the posterior part of the intestine in Lineus gesserensis ; 

 and this phenomenon was present, and better marked, in Cephalothrix linearis. In 

 this species the waves are sometimes sudden and sharp, at other times slow ; they 

 are capable of forcing solid masses up the gut for some distance ; they are not, 

 however, continuous over long distances, but are rather fragmentary, each one 

 being confined to a limited portion of the tract. Direct peristalsis occasionally occurs, 

 but is much less frequent. 



These observations are of interest, because Cephalothrix is perhaps one of the most 

 primitive genera of Nemertines, and because it is the one in which the blood-vessels 

 also are most obviously contractile. 



Summary. 



One or more species belonging to each of nineteen families of Polychseta were 

 submitted to examination. The main results of the observations may be outlined in the 

 table which follows (p. 810). 



This table may be compared with that constructed for the aquatic Oligochseta 

 (p. 744). A few remarks on certain points may be added. 



(1) In considering the frequency of ascending ciliary action in the intestine, it is 

 necessary to exclude from the enumeration several of the above families. In the 

 Arenicolidse, Flabelligeridse, and Cirratulidse, the conditions (size, opacity, contraction 

 of intestinal canal) did not allow of observation of the interior of the intestine ; all that 

 can be said is that there is a slight probability in favour of its occurring in the 

 Cirratulidse, and no reason either for or against in the other two families. In the 



