INTESTINAL RESPIRATION IN ANNELIDS. 807 



Eriographid^. 



Myxicola dinardensis. 



Ciliary motion was observed in this species throughout the greater part of the 

 intestine, from the anus to the beginning of the stomachal dilatation ; in places it was 

 indefinite in direction, but on the whole it was, as usual, ascending. The anus was 

 closed during the time of examination ; it is perhaps a fair assumption that if it had 

 been open the ciliary action would have been much more obvious and definite. 



Antiperistalsis was observed to extend throughout the intestine, as far forwards as 

 the second setigerous segment. Its character varied at different times and in diff'erent 

 regions ; at times a regular and fairly strong series of contractions in the middle region 

 of the body markedly constricted the lumen of the intestinal canal ; at other times 

 their effect was confined to the perienteric sinus, the lumen of the gut being scarcely 

 narrowed at all. 



The physiological importance of the posterior end of the body is as marked as in 

 Potamilla. In addition to the lateral rows of eye-spots, the animal possesses a pair of 

 clusters of such spots at its anal end. This end, too, resembles a worm's head in shape ; 

 the animal continually uses it for exploration, turning it from side to side, retracting it, 

 trying another direction, exactly as a worm does with its head. The animal always 

 crawls with this end in advance ; indeed, the posterior end obviously is, in a physiological 

 sense, the animal's head ; the other end, the morphological head, is merely dragged 

 behind, and is quite passive. It may be added that Benham (4) states that 

 M. infundibulwm also moves tail first. 



Serpulid^. 

 Spiror'his horealis. 



Ascending ciliary action was seen in all the specimens examined. As an example, 

 the appearances may be described in an animal in which the alimentary canal was at 

 first in a contracted condition in the whole of its posterior portion. Though violent 

 ciliary action was observed outside the anus, none could be seen inside the intestine, 

 and, the anus being closed, no carmine particles were taken in. After some time the 

 anus opened, and a violent ascending ciliary action was then visible in the intestine. 

 By varying the focus of the microscope, currents to and from the anus could be seen ; 

 at one level, all the carmine particles were being swept towards the anus ; at another, 

 the motion of the particles was for the most part directed away from the anus. A few 

 carmine particles were seen to enter the intestine, but they never seemed to ascend 

 very far, and were usually soon rejected ; the animals often give the observer the 

 impression that they shrink from the touch of solid particles. It may perhaps be 

 inferred that the anus is normally used for the ingestion of fluid only (cf. Polycirrus). 

 Similar phenomena were noted in other specimens. In one, a mass of fseces in the 

 TRANS. ROY. SOC. EDIN., VOL. XLIX. PART IH. (NO. 14). 110 



