INTESTINAL RESPIRATION IN ANNELIDS. 743 



iEoLOSOMATID^. 



jEolosoma viride Stephenson. 



When I first described this form (46) I was inclined to think that it might be 

 possible to unite it with A. Headleiji Bedd. ; further study has, however, convinced 

 me that differences of colour, of shape of the cerebral ganglion, of the number of 

 nephridia, and especially of the form of the setae, require that it should be considered 

 as specifically distinct. 



Antiperistaltic movements occur constantly, often at the rate of about forty per 

 minute. The waves may include the stomach, as well as the whole length of the 

 intestine ; or, while some include the stomach, others may cease at its posterior end. 



Ascending ciliary action occurs in the intestine, and is often very distinct and 

 violent in its posterior part. 



y^olosoma hemprichi Ehrbg. 



In the form which I have tentatively identified as above (47), the antiperistalsis is 

 commonly, though not always, confined to the dilated portion of the alimentary canal 

 in about the middle third of the length of the animal, which may be called the stomach. 

 In one case the antiperistalsis was obvious in the posterior two-thirds of the stomach, 

 while a direct (antero-posterior) peristalsis occurred in the anterior third ; the two 

 waves meeting, the antiperistaltic overcame the direct wave, and then continued 

 forwards to the anterior end of the stomach. 



Ascending ciliary action also occurs in the intestine, and may be very distinct and 

 violent, so as to be easily visible with the low power. Though as a rule confined to the 

 posterior part of the alimentary canal, it may extend into the stomach ; but often the 

 ciliary motion in the stomach, though distinct, is indefinite in direction, or it may be 

 antero-posterior. Small algal bodies may be carried upwards for a short distance along 

 the alimentary tract, i.e. postero-anteriorly, by means of the ciliary current, and food- 

 remains may also be swept in the same direction by the same force. 



Experiments with carmine particles were made in an animal which was exhibiting 

 violent ciliary motion. Particles were taken into the intestine through the anus by 

 ciliary action, and were carried upwards for a short distance. They were then arrested, 

 and moved alternately a little upwards and a little downwards for some time, and 

 finally were quickly shot out through the anus. The antiperistaltic movements 

 of the gut assisted the particles in ascending the intestine ; but none ever seemed 

 to get up for a distance of more than two or three times the diameter of the 

 animal's body. 



In this species I paid some attention to the motion of the food-matter in the 

 alimentary canal. The contents of the intestine were often moved round and round in 

 a rotatory manner about an axis coinciding in direction with the axis of the gut. This 

 rotatory movement occurred while the cilia were working in the usual postero-anterior 



TEANS. ROY. SOC. EDIN., VOL. XLIX. PART III. (NO. 14). 102 



