The behavior of the doublet of Oxytricha bifaria (Ciliata, Hypotrichida): A contribution to the understanding of this enigmatic form

The tracks of normal organisms of Oxytricha bifaria and of stage IA, IB, II , III, IV and V doublers were studied to test the hypothesis that the doubl er might function as a dispersal form. Stage IA, the only stage to swim, sw ims straight with only rare interruptions: its rate of mobility (R-mo = 443 mu/s) is roughly twice that of singlets (R-mo = 218 mu/s) Stage IA doubler s swim in three-dimensional movement which enables them to be carried away by water currents. The other stages seem to represent passage back towards the normal singlet form. The ethological evidence reported here together wi th other results already published supports the working hypothesis that the doubler of O. bifaria is a dispersal form suggests that the doubler might well represent a special fourth differentiation state of this species in ad dition to pairs, giants, and cysts.