810 



PROFESSOR J. STEPHENSON ON 



Spionida3 I have unfortunately no note as to whether it occurs or not. Excluding these 

 four families, the phenomenon occurs, not in all, but in some, members of eleven 

 families out of fifteen. 



This, however, very possibly understates the case. The phenomenon is variable — 

 sometimes absent or ill marked, and sometimes well marked, in the same species, or 

 even in the same specimen ; and it may occur in one species, and not (so far as observed) 

 in a related species {e.g. among the Syllida?). It is possible, therefore, that it might 

 have been observed in families in which it is recorded as absent, if other species or even 

 other specimens of the same species had been examined. 



The ascending ciliary action is often visible when the anus is closed, and may even 

 be distinguishable when, in addition, the intestine is itself so much contracted as almost 

 to occlude the lumen. It is, however, usually much more marked when the anus is 

 open (e.g. Odontosyllis, Castalia, Capitella, Potamilla, Spirorbis, Poniatoceros) ; and 

 sometimes, as for example in Castalia punctata, the relaxation of the anus, in a 

 specimen in which it has been closed for some time, resembles nothing so much as the 

 opening of sluice-gates in a watercourse. 



That the effect of the ciliary action is to produce an upward current in the fluid 

 contents of the alimentary canal, and to cause the entry of water at the anus, if the 

 anus is open, will be at once admitted. The appearances are conclusive to anyone who 

 examines such forms as Castalia, Capitella, Chietoptcnis, and certain Syllids, Sabellids, 

 and Serpulids, or who has tried the carmine experiment with Ammotrypane, Melinna, 



