THE BOTTLE ANIMALCULE, FOLLICULIXA. 2J3 



of thus, as it were, feeling about, the Folliculina swims away from 

 the tube, as in the upper part of Fig. I and then resembles a 

 spirostomum. It may sooner or later settle upon leaf or stem 

 and glide about, as in the bottom of Fig. I, resembling then a 

 planarian in motion. \Yhile very often an elongated cylinder it 

 changes in swimming or gliding to various shapes, bending and 

 contracting, may often assume a bottle form from the swelling 

 of the posterior end, become flattened or take the form of a 

 spheroid. The body is generally dark blue-green with the 

 anterior part frequently much darker than the rest since a short 

 region back of the truncated end is sharply set off as almost 

 black and very opaque. The posterior end is frequently dark 

 also. 



The form assumed is often that of some species of Stentor 

 in motion, and study of compressed living as well as sectioned 

 material shows that they have the organization of Stentor 

 cosruleus as described by Schroeder and verified by me on the 

 same form for comparison; but they present certain marked 

 simplifications at the anterior end and a complexity at the pos- 

 terior end that w r ill be elsewhere described. 



These swimming forms show r a great diversity in size as well 

 as in form and in color density. Often they measure about one 

 half millimeter .in length. 



The locomotion seems due to the longitudinal rows of cilia 

 that cover the body and not to the abbreviated spiral of mem- 

 branellae at the anterior end. They swim forward with rotation, 

 the right side coming up and over to the left, probably four to 

 five times a second. The speed is two to four millimeters per 

 second, but it changes. After long continuous stretches of 

 motion it may advance, with interruption in jerks, as if the cilia 

 stopped and resumed. Frequently the direction is changed and 

 the phenomena of reversal and advance in another direction on 

 approaching the edge of the water seem like those of Paramtrcium. 

 While the trajectory appears straight, often, it may again be a 

 long sinuous curve and often a spiral. After stopping the animal 

 may turn off and progress at an angle with its former course, as 

 above stated, or it may move backwards nearly on its trail. It 

 may reverse, spin on its transverse axis and then resume the old 

 direction. 



