INTESTINAL RESPIRATION IN ANNELIDS. 805 



Genus Terehella. 



A number of young specimens of T. nebulosa, found at Millport, were small enough 

 to be examined microscopically. 



In the specimen in which the appearances were best marked, ciliary motion was not 

 seen within the intestine ; round the anus, however, it was obvious, and though it did 

 not seem to give rise to a current in any definite direction, some small particles appeared 

 to enter the anus, which was held open. 



Antiperistaltic contractions began at the anus and extended the whole length of the 

 intestine ; they were slow and fairly ample. A perienteric sinus is present in the walls 

 of the gut, very narrow posteriorly, but wider in the anterior part of the intestine ; in 

 this latter region the lumen of the gut is not affected by the contractions of the 

 muscular coat, which thus act only on the fluid contained in the sinus ; in the posterior 

 region the contractions are not merely circulatory in their effect, since here they also 

 cause a narrowing of the lumen of the intestine. 



T. lapidaria, examined at Plymouth, shows no definite evidence of any intake of 

 fluid ; a few carmine particles entered the anus, but their entry seemed to be a matter 

 of chance. 



Ampharetid^. 



Melinna sp. 



A number of examples of a species of Melinna were observed at Plymouth. 



iVscending ciliary action may be seen just within the anus ; the animals are too 

 opaque to allow of its being followed far, but it can be successfully demonstrated by 

 the carmine experiment. The anus is frequently held open ; and at such times carmine 

 particles may be seen slowly to approach the anus, and then rapidly to enter ; particles 

 resting on the surface of the body near the posterior end may be seen to move back- 

 wards in a line, as if connected together by an invisible thread, and then to round the 

 hinder end of the animal and enter the anus, travelling along and clinging to the 

 surface all the way. 



Antiperistaltic contractions of the intestine may also be observed in the posterior and 

 middle regions of the body. They may begin at the anus, or at a more anterior point. 

 In the specimens observed, which had been in the laboratory for over a week, they 

 were irregular in rhythm. 



Sabellid^. 



Genus Potamilla. 



Examples of two small species of Potamilla were examined at Plymouth ; the 

 larger of the two was perhaps P. reniformis, the smaller probably P. torelli. 



In the smaller of the two species ascending ciliary action was observed in the 

 majority of specimens. In one case it was well marked, indeed violent, in the last three 



