808 PROFESSOR J. STEPHENSON ON 



posterior part of the intestine was seen to be continually rotating round the longitudinal 

 axis of the canal (cf. jEolosoma viride, p. 744 ante). 



No antiperistalsis was observed in any of the specimens. It must however occur, 

 at least in the form of contractions of the gut- wall which effect the circulation in the 

 perienteric sinus ; Fuchs (19) speaks of a contractile intestinal sinus in this family. 



Pomatoccros triqueter. 



This species is too opaque to be easily examined. Ascending ciliary action may 

 however be seen at and for a short distance above the anus, even though the anus and 

 lumen of the intestine are much contracted. In one specimen the anus was seen to 

 open and close from time to time — about eight times per minute, but irregularly — and 

 the ascending ciliary action was more easily to be observed while the anus was open. 



Intestinal antiperistalsis occurs, but in different degrees at different times and places ; 

 in the posterior part of the body it was, in one specimen, circulatory only in its effect, 

 i.e., while causing constriction or obliteration of the perienteric sinus, it did not influence 

 the calibre of the intestinal lumen ; in the middle region of the body of another 

 specimen, however, it caused a marked narrowing of the lumen of the canal. 



Addendum on Similar Phenomena in certain other Groups. 



1 subjoin a few observations on related groups, made in the course of my work as 

 opportunity offered. 



Ai^chiannelida. 



During my stay at Plymouth I was kindly supplied with specimens of Dinophilus 

 twniatus and Histriohdella homari. 



Dinophilus tmniatus, though a small animal, is very opaque, and the observation of 

 the interior of the alimentary tract is not easy. Ascending ciliary motion was observed 

 in a number of specimens, but it was never as obvious or as violent as in certain of the 

 Polychseta or Oligochseta. 



As an example, a specimen may be cited which showed this phenomenon for a 

 considerable distance up the alimentary canal from the anus ; for a short space above 

 this, ciliary motion was present in ati ascending direction on the left side of the intestine, 

 in a descending direction on the right ; and just behind the stomach it was entirely 

 descending. Later, this ciliary action was ascending in direction in the anterior part 

 of the intestine, especially at the junction of intestine and stomach, but near the anus 

 its direction was indefinite. 



Many variations were met with, especially with regard to the extent and direction 

 of the ciliary currents in the stomach and anterior portion of the intestine. In some 

 cases no ciliary motion could be detected, but this was, in all but one specimen, because 

 the intestine was full of solid matter. 



