806 PROFESSOR J. STEPHENSON ON 



and a half segments : the anus was open, and the lumen of the gut widely patent. 

 Small particles were carried into and rapidly up the intestine, then were forced 

 downwards for some distance, again carried up, and so on ; the downward recoil 

 of the particles was apparently due to a series of spasmodic contractions of the 

 intestinal wall in the fourth segment from the end ; the whole of the rest of the 

 canal in this specimen was altogether quiescent. In other cases, for example those 

 in which the anus was kept closed during the examination, ciliary motion was feeble 

 or absent. 



Antiperistaltic contractions of the intestine are almost always to be observed ; they 

 are usually only circulatory in their eflfect, i.e. they affect only the contents of the 

 perienteric sinus, and are not violent enough to cause any narrowing of the lumen of 

 the alimentary canal. The contractions may extend in regular series over the whole 

 intestine to within a short distance of the head ; or they may be irregular and 

 discontinuous. 



In the larger of the two species the anus was, in the specimens examined, kept 

 closed and the lumen of the posterior part of the gut almost occluded. Eeversed ciliary 

 action was not observed. The antiperistaltic contractions of the intestine were circula- 

 tory only in their effect, and had no influence on the already contracted lumen of the 

 gut. Two striking peculiarities of this animal, which must impress every observer, are 

 its mode of locomotion, and the use it makes of its posterior end in exploration. There 

 are two clusters of small eye-spots, one on each side of the anus ; this end of the body 

 is continually active, exploring in all directions, and it is always this end which it pro- 

 trudes, when possible, from under the edge of the cover-slip. This, and the continual 

 slow-crawling locomotion, always with the anal end first, unite in making it appear 

 as if this were the anterior end of the worm ; while the gills — dragged behind, folded 

 like a closed umbrella — seem like projections from its hinder end. 



Dasychone homhyx. 



The phenomena are similar to those in Potamilla. A reversed ciliary movement 

 could be followed from the anus upwards for about six segments, though the posterior 

 part of the intestine was considerably contracted ; small particles were seen to be taken 

 in at the anus. The antiperistaltic contractions (in this condition of the intestine at 

 least) are entirely circulatory in their effect. 



In some Sabellids examined at Millport, but not identified, similar phenomena were 

 observed. Ascending ciliary movement was present, either restricted to the most 

 posterior section of the intestine, or extending upwards through its hinder and middle 

 thirds, — in the latter case, violent at its hinder end, and visible even when the worm was 

 viewed as an opaque object under the low power of the binocular. Autiperistalsis was 

 present over the whole intestine, or was absent in its middle third ; in any case, its 

 effect was mainly circulatory. 



