584 ORDER HETEROTRICHA. 



Genus I. CONDYLOSTOMA, Dujardin. 



Animalcules free- swimming, changeable in form, ovate or elongate 

 almost cylindrical, slightly flattened and obliquely truncate anteriorly ; the 

 peristome-field restricted to the anterior extremity of the body, presenting 

 the aspect of a harp-shaped excavation, the upper and outer or left-side 

 border of which bears the strong adoral cilia, while from its entire inner 

 or right margin is produced a flap-like undulating membrane ; endoplast 

 elongate, moniliform ; contractile vesicle single or multiple, sometimes 

 associated with elongate canal-like extensions ; anal aperture postero- 

 terminal. Inhabiting salt and fresh water. 



Condylostoma patens, Miill. sp. Pl. XXIX. Fig. 12. 



Body highly elastic, elongate-elliptical or ribbon-shaped, more or less 

 undulate, nearly cylindrical, its length when extended equal to seven or 

 eight times its greatest breadth, widest posteriorly, somewhat flattened 

 anteriorly, slightly contracted behind the region of the peristome ; 

 peristome-field consisting of an irregularly triangular or harp-shaped ex- 

 cavation occupying an almost median position at the anterior extremity of 

 the ventral surface, its length equal to about from one-fifth to one-sixth of 

 the entire body, succeeded by a narrow tubular pharynx equal to one-half 

 the length of the peristome ; undulating membrane conspicuous, extending 

 over the whole length of the right side of the peristome-border, its width 

 equal to one-half of that of the peristome-field ; peristome-field unciliated, 

 very transparent ; cuticular striae fine, distributed equally and in parallel 

 longitudinal lines throughout the surface of the body ; endoplast elongate, 

 moniliform, located towards the right side ; contractile vesicle canal-like, 

 often breaking up into vesicular spaces that extend along the entire left 

 border of the animalcule. Length of extended body 1-72" to 1-48". 



Hab. — Sea water. 



This animalcule was first figured and described by O. F. Miiller as a species 

 of Trichoda, its present generic title being conferred upon it by Dujardin. Claparbde 

 and Lachmann have proposed to add a new species to the genus Condylostojna 

 under the title of C. patulum. As shown by Stein, however, there does not appear 

 to be sufficient evidence to permit of this type being regarded as otherwise than 

 identical with one of the many protean forms assumed by C. patens. 



Condylostoma stagnale, Wrz. Pl. XXIX, Fig. ii. 



Body slightly contractile only, broadly ovate, not twice as long as 

 broad, rounded and widest posteriorly, the anterior border obliquely 

 truncate ; peristome-field broadly triangular, extending backwards through 

 nearly one-half of the length of the body, its right border bearing a well- 

 developed undulating membrane, its left one a vigorous fringe of large 

 adoral cilia ; longitudinal muscular fibrillae large and coarse ; contractile 

 vesicle presenting the form of an irregular-shaped vacuole at the posterior 

 extremity; endoplast elongate, moniliform. Length 125". 



Hab. — Stagnant water. 



