88 DAVENPORT ACADEMY OF SCIENCES. 



are seen in a single drop of water, darting about and suddenly 

 coming to rest like so many flies. 



Reproduction takes place rapidly by transverse division. 



CTEDOCTEMA Stokes. 



Elongate-oval, cilia of the general surface long and rigid, with 

 a longer seta projecting from the posterior border. Oral groove 

 long and narrow with a series of long, curved setae on the right- 

 hand border. Oral aperture at the posterior end of the groove. 

 Nucleus single, in the anterior region. Contractile vesicle single 

 in the posterior region. Trichocysts abundant. 



Ctedoctema acanthocrypta Stokes. 



Body ovate, wider posteriorly. Cilia long, rigid, with a longer 

 hair-like seta, curved at the distal end, projecting from the pos- 

 terior border. Oral aperture at the posterior end of a shallow 

 ventral groove which extends nearly the entire length of the body. 

 From the right-hand margin of the groove extends a series of long 

 rigid cilia gradually diminishing in length as they approach the 

 oral aperture. From the left-hand margin of the groove extends 

 a series of line vibratile cilia also decreasing in length posteriorly. 

 Nucleus oval in the anterior extremity of the body. Contractile 

 vesicle posterior. Trichocysts very numerous. 



Eength of body, 25 microns. (Fig. 143, PI. XIX.) 



This species has been found abundantly in Johnson county 

 among fresh water algae. In general contour the body somewhat 

 resembles Cj r/idiu m . 



On the lateral border near the posterior extremity of the body 

 there may at times be seen a bubble-like outpushing of the proto- 

 plasm, but the ectoplasm apparently does not burst as, in a short 

 time, the protruded portion is withdrawn, the phenomenon soon to 

 be repeated. 



The distal ends of the rigid cilia bordering the ventral groove 

 adhere, giving the appearance under low magnification of a long, 

 recurved seta arising from the posterior end of the groove. 



Chemical stimuli may cau.se the trichocysts to be extended. 

 They are stout, about 15 microns in length, and appear to be 

 thickened at the distal end. This thickening, according to 

 Stokes who discovered and described the species, is due to minute 



