628 



ORDER PERITRICHA. 



petaloid modification of the peristomal border, it would seem to most nearly 

 approach Haeckel's genus Codonella. In, however, the possession of a distinct pha- 

 ryngeal pouch, which, in accordance with Professor Fol's delineation, Woodcut, 

 Fig. i, ph, stands out separate from the body like the gibbous pouch or spur of a 

 floral envelope, this type has no parallel among the entire infusorial series. Professor 

 Fol's general account of this new type runs as follows : 



FIGS, i and a. Petalotricha. ampulla, Fol sp. i. Lateral aspect, showing at//4 pharyngeal pouch, X 300. 2. Two 

 conjugating zooids viewed from above; or, oral aperture ; ep, raised boss or epistome. 

 FIG. 3. Petalotricha spiralis, Fol sp., X 200. {After Professor Fol.) 



" The superior discoidal extremity or peristome, when the animal is in a state 

 of perfect extension, is placed a little obliquely with relation to the aperture of the 

 test. The disc itself, instead of being flat or slightly convex, as is the case in the 

 Vorticellina, is hollowed out like a saucer, and the vibratile cilia, instead of forming 

 a single row round the margin of the disc, are implanted in great number and in 

 several lines over the greater part of the surface. The arrangement of these vibratile 

 cilia is exceedingly curious and interesting, and deserves attention, the more because 

 it has not been described by any of the authors who have busied themselves with the 

 Tintinni. The whole margin of the disc is occupied by long and strong motor cilia, 

 which strike the water vigorously, and give the animal an exceedingly rapid recti- 

 linear movement of translation. It is thus, in fact, that the animals habitually swim; 

 but they can readily deviate from the direct line when they have to avoid an obstacle. 

 Moreover, the animal is constantly turning upon itself during its progress, which is 

 therefore comparable to that of a rifle ball. As soon as the great motor cilia com- 

 mence their action, they present the so-called phenomenon of rotation in a high 

 degree. The undulation is propagated from right to left, the observer being supposed 

 to be placed at the axis of the animal. The other cilia are arranged in parallel lines, 

 all curved in the same direction, and running from the margin of the disc or 

 peristome towards the mouth. In the present species, T. ampulla, twenty-four of 

 these lines were counted. The mouth occupying an eccentric position, or Fig. 2, 

 the lines which start from the margin nearest to that aperture are of course much 

 shorter than those which start from the more distant margin. There are, however, 



