736 PROFESSOR J. STEPHENSON ON 



the other hand, which have for their basis the phenomena and the facts of distribution 

 of intestinal respiration, come most fittingly at the conclusion of the paper. 



I wish here to express my sincere thanks to Mr R. Elmhirst, Superintendent of 

 the Millport Marine Biological Station, and to Dr E. J. Allen, Director of the Plymouth 

 Marine Laboratory, for the facilities and assistance so readily afforded me in my work 

 at these places. My best thanks are also due to the Senate of the University of 

 London for permission to occupy the University table at Plymouth for a month 

 during the summer of 1912. 



L OLTGOCHiETA. 



1. The Phenomena of Antiperistalsts and Ascending Ciliary Action 

 IN THE Intestine of Aquatic Oligoch^ta. 



If one of the smaller aquatic Oligochseta, such as a Nais or Pristina, be placed under 

 the microscope and observed for a few minutes under a low power, the posterior part, 

 or even in many cases the whole length of the intestine, will be seen to manifest 

 recurring contractions, which constrict the lumen, and passing forwards in succession 

 from the posterior towards the anterior end, die away, perhaps about the region of 

 the stomach, perhaps some distance before reaching this point. These contractions 

 are of the nature of those known as peristaltic ; but since they always occur in a direction 

 from behind forwards, and not from in front backwards, they may, borrowing a term 

 from mammalian physiology, be better described as an antiperistalsis. 



If the intestine itself be now more minutely examined — and though the phenomenon 

 is often visible with a low power, it is at any rate more obvious with a high one — • 

 ciliary motion will probably be seen to be actively going on within the lumen of the 

 canal. The direction of action of the cilia is obviously, like that of the antiperistaltic 

 contractions, from behind forwards ; the anus will probably be open, and if some 

 particles of carmine be added under the coverslip, these may be seen to be swept in, 

 and thence upwards along the alimentary canal for some distance. 



These or similar phenomena have been known for some time among the Polychseta ; 

 and it is generally recognised that, in many animals of that Order, the intestine has 

 a respiratory function. In the Oligochseta, the phenomena have not received much 

 attention. Antiperistaltic movements of the intestine in Enchytrseids have been 

 described by Vejdovsky (53, p. 33), and are referred to by Michaelsen (32, p. 28) ; 

 these authors are quoted by Lang (29, pp. 211, 212). Bousfield (9) speaks of the 

 intestine in the genus Dero as " having a very strong inward ciliary current for a 

 great part of its length,'' and adds, " in all the Oligochseta a strong inward current is 

 visible in the hinder part of the intestine, which, no doubt, subserves a respiratory 

 purpose, as it commences at the point where the arterial system receives its blood from 

 the venous." Hesse (24) mentions this as a characteristic of the Naididse. Neither 

 Vejdovsky (54) nor Beddard (3) refer to the phenomena in their monographs on the 



