802 PROFESSOR J. STEPHENSON ON 



Ciliary motion in the intestine of course could not be made out. 



The anus may be seen, in specimens under observation in a dish, to be periodically 

 held open, sometimes widely, then closed, opened again for a time, closed, and so on. 

 The animal may at the same time continue pushing its hinder end about, as if it were 

 using it to explore with. 



In the middle part of the body, which is fairly transparent under pressure, a well- 

 marked antiperistalsis of the intestine was noted ; in a second specimen this manifested 

 itself as a continuous antiperistaltic ripple, which began gently about segment xviii. 

 and ended at about segment vi., behind the pharynx. Antiperistaltic contractions were 

 never observed in the hinder part of the intestine ; possibly because most of the speci- 

 mens were quite opaque here, and so could not have manifested it in any case. Hence, 

 though the observer receives the impression that " mouthfuls '" of water are being taken 

 in at the anus, the proof that any water is passed up the intestine by antiperistalsis is 

 wanting. The description may, however, be compared with what happens in Leptonereis 

 and Capitella (pp. 799 and 803). 



The antiperistalsis is unconnected with the vascular contractions ; these are more 

 frequent, and pass along much more rapidly. 



Flabelligerid^. 

 Siphonostormi diplochaitos. 



In the single specimen of this worm which I have had the opportunity of observing, 

 the anus was held open, but the lumen of the gut was contracted — it might be said to 

 be absent. It was therefore impossible to say whether an ascending ciliary action ever 

 occurred or not. There was no evidence of any ciliary movement outside the anus. 



A perienteric sinus surrounds the intestine, and this, in the compressed animal, was 

 much wider than the proper alimentary tube within it.* 



A well-marked antiperistalsis, regular, rapid, and frequent, began at the anus. The 

 lumen of the intestine being already constricted to the point of disappearance, this 

 could obviously not affect the diameter of the canal, and could subserve only the pro- 

 pulsion of the fluid in the sinus; but presumably at other times the condition would 

 be that of the Enchytrseidse or of iEolosoma {cf. pp. 749, 751, 752), where alimentary 

 antiperistalsis and vascular contractions are one and the same thing. The anatomical 

 relations also correspond to those of the Enehytrseidae : there is no dorsal vessel in the 

 intestinal region, but the ventral vessel extends to the hinder end of the body 



Capitellid^. 

 Capitella capitata. 

 The anatomy and physiology of the accessory intestine have been described, in 

 accordance with Eisig's account, in the historical section. My observations do not 



* FucHS (19), describing the vascular system of this worm from a paper by Jaquet, speaks of lacunas in the 

 intestinal wall, but says that he is unable to make out from that author whetlier tliere is a perienteric sinus or not. 



