112 DAVENPORT ACADEMY OF SCIENCES. 



colony falls down, the physiological condition apparently result- 

 ing in a weakening of the supporting pedicels and branches. Fig. 

 203, PI. XXVIII, from a prepared mount, shows the ciliary con- 

 volutions of the oral system. As in other colonial forms of this 

 family the zooids may develop a posterior wreath of cilia, break 

 away from their pedicles and, each leading an independent life 

 for a time, may ultimately settle down in more favorable condi- 

 tions and begin the development of a new colony. 



The species is not uncommon in the waters of this state, usu- 

 ally found abundantly in small running streams or fresh water 

 pools, attached to leaves, sticks, rocks, etc. 



Epistylis articulata From. 



Zooids elongate, dilated anteriorly, tapering toward the pos- 

 terior extremity; surface smooth. Stalks short and stout, longi- 

 tudinally striate, dichotomously branching, with an articulation 

 near the middle of the main pedicle and sometimes one or two 

 between each bifurcation of the branches. 



lyength of zooids, 42 microns. 



Figure 197, Plate XXVII, represents this species, being a young 

 colony with two zooids. Figure 198 illustrates the colony in the 

 process of growth by longitudinal division, the zooids being con- 

 tracted. 



Figure 199 pictures a single zooid in a contracted state, oval in 

 form, with a concave depression in the anterior border, but lack- 

 ing the annular furrows of the posterior region which are present 

 in Epistylis plicatilis. The colonies are small, containing not more 

 than a dozen zooids, and the more frequent number is from four 

 to six. 



Found in Johnson county, attached to rocks in a small running 

 stream. 



Epistylis plicatilis Ehr. 



Zooids elongate, conical, with anterior border dilated and cil- 

 iary disc elevated. Surface smooth; when contracted, deep annu- 

 lations occur in the posterior region while the anterior border is 

 often drawn into a minute cylindrical process. Stalk slender, 

 dichotomously branched, secondary divisions very long. 



Nucleus band-like, curved. 



Eength of zooids, 75-100 microns. (Figs. 200-201, PI. XXVIII.) 



