92 DAVENPORT ACADEMY OF SCIENCES. 



occupying the posterior extremity and extending forward, canal- 

 like, nearly to the anterior end. 



lycngth of the extended body, 500-2800 microns. (Fig. 148, 

 PI. XX.) 



SpirosfonmiH ambigunm, which is one of the most elongated 

 free-swimming ciliates known, is a' very common species in pond 

 water among aquatic plants. The organism is extremely .sensi- 

 tive, quickly contracting into a short, spiral body on the slightest 

 disturbance. Fig. 149. 



Reproduction is by transverse division. 



Spirostomum teres C. & L. 



Differing from Spirostoniinu ambiguiini in the following char- 

 acters: Body shorter and narrower. Oral furrow not so long in 

 proportion to the length of the body. Nucleus oval, centrally 

 located. 



Length of extended bod}^ 300-500 microns. (Fig. 150, 

 PI. XX.) 



Very commonh' associated with the last named species. 



Family, BURSARID^. 



CONDYLOSTOMA Dujardin. 



Ovate or elongate, cylindrical. Peristome short in proportion 

 to the length of the body, provided with an undulating membrane 

 and strong cilia. Nucleus moniliform, elongated. Contractile 

 vesicles often numerous. 



CONDYLOSTOMA Sp. 



Body elongate, cjdindrical, and somewhat elastic, rounded 

 posteriorly, posterior extremity abruptly curved toward the ven- 

 tral aspect and terminating in an acutely pointed tip. Peris- 

 tome, a furrow-like depression extending about one-sixth the 

 length of the -body, bearing on the right side an undulating 

 membrane, on the left margin a series of strong cilia. Nucleus 

 moniliform, elongated, ventral in position. Contractile vesicles 

 more than one. 



Length, 150-200 microns. (Fig. 151, PI. XX.) 

 Figure 151 was taken from a fixed specimen slightly contracted, 

 the normal individual being somewhat more elongated than is 



