EDMONDSON — PROTOZOA OF IOWA. I07 



wreath of cilia, swims away and settles down, developing a stalk 

 of its own. Thus the cycle of life repeats itself. 



When conditions are unfavorable normal individuals may de- 

 velop a posterior circle of cilia, break from their pedicels and swim 

 away to form another stalk under more fav^orable surroundings. 



Conjugation in this group consists of a permanent union of two 

 individuals, the larger, attached macrogamete and the smaller 

 free-swimming microgamete, which attaches itself to the body of 

 the stalked form. On one occasion, as observed by the writer, 

 the complete absorption of the microgamete required eight hours. 



VORTICEI.LA CAMPANULA Ehr. 



Body broadl}' campanulate, greatly dilated anteriorly, surface 

 smooth. Stalk thick, usually five or six times the length of the 

 body. Endoplasm dark granular, often opaque. 



Length of body, 150 microns. (Fig. 182, PI. XXV.) 

 A common species in pond water, also found in great social 

 groups on the under side of stones, leaves, etc., in small running 

 streams. The collared flagellate, Monosiga steinii, is often attached 

 to the pedicle of this species. 



VORTICELLA NUTANS Miill. 



Body campanulate, dilated anteriorly, surface smooth. Stalk 

 slender, three or four times as long as the body. Endoplasm 

 usually transparent. During extension the body is recurved to- 

 ward the base of the stalk. 



Length of body^ 80 microns. (Fig. 183, PI. XXV.) 



Found in pond water in social groups. 



VoRTicELLA ALBA From. 



Body oval, wider centrally, anterior border not greatly dilated, 

 surface smooth. Stalk short, about three times the length of the 

 body. Endoplasm transparent. 



Length of body, 55 microns. (Fig. 184, PI. XXV.) 



Found in social groups in pond water. 



VORTICELLA LONGIFILUM S. K. 



Body elongate, anterior border not widel}^ dilated. Surface 

 smooth. Stalk slender, from twelve to fifteen times the length of 

 the body. 



