742 PROFESSOR J. STEPHENSON ON 



In general, antiperistalsis proceeds continually and fairly regularly, beginning at 

 or near the hinder end of the animal, and ending near the anterior limit of the intestine. 

 As will be seen more fully later, this antiperistalsis serves to propel the blood in the 

 intestinal plexus (or sinus) ; and its anterior limit corresponds in general to the point 

 where the plexus or sinus passes into the dorsal vessel, which in this family exists only 

 in the anterior part of the body ; this point varies in its situation within fairly wide 

 limits in the different genera and species. 



Reversed ciliary action is in general not present. 



Several observations may be cited, which illustrate the kind of phenomena occurring 

 in this family, and at the same time show a few variations from the typical order. 



Lumbricillus tuba Stephenson (50). 



Antiperistalsis may begin from a point very near the posterior end of the animal, 

 or from a point in front of this e.g. about nine segments from the end. In one case 

 the contractile wave originated from a point corresponding to the septum between 

 the eleventh and twelfth segments, reckoning from the hinder end ; but in this case 

 the wave was propagated in both directions : anteriorW in the usual manner, and 

 posteriorly for a few segments as a direct peristalsis, as far as about the eighth 

 segment from the hinder end. 



The rate was in one case seen to be seven per minute. 



Enchytr^ns alhidus Henle. 



Here, again, the antiperistalsis, where it fails, does so at the hinder end, as is 

 illustrated in the following two observations out of several : — 



In one example antiperistalsis was absent in the last fourteen segments, was faint 

 in front of this, and further forwards still was quite well marked. The rate of the 

 contractions was five in two minutes, but the intervals were very irregular. 



In a second specimen antiperistalsis began a short distance in front of the anus ; 

 the waves passed forwards slowly, traversing the high-power field of the microscope in 

 twenty seconds, and the contractions were not very ample. Further forwards the 

 waves increased in rapidity and strength ; they were observed here to pass across the 

 high-power field in ten .seconds. 



Fridericia bulhosa (Rosa). 



This is the only Enchytneid in which I have observed the reversed ciliary action in 

 the gut whicli is so common in the other lower Oligochseta. I saw it in one specimen 

 only, in the eighth and ninth segments from the hinder end. In front of this point, 

 and behind it, ciliary motion could be seen, but it was indefinite in direction ; it was 

 not to be observed at all over the greater part of the alimentary canal. 



