AND PHYSIOLOGY OF TEICHODINA. 119 



a single row of cilia (g) ; both of which serve to heighten its conspicuity, and give to 

 this region of the body the appearance of greater weight and firmness. 



§ 4. The Prehensile Organs. 



The motory organs appear to be divided into two groups, of which one is very active in 

 character, and the other is comparatively passive and resistant. The members of the 

 former group are the vibratile cilia and velum, and those of the latter constitute the "adhe- 

 rent organ." 



The vibratory crown. The vibratile cilia occupy two widely separate parts of the bodjr, 

 in one place fulfilling the office of purveyors of food, and in the other acting as organs of 

 locomotion, in the strictest sense. The former are the true prehensile organs, and, with 

 the margin to which they are attached, constitute the so-called "vibrator// crown" (b, b l , b 2 ). 

 This organ lies, in the form of a nearly flat spiral, at the anterior end of the bod}', and 

 borders the edge of the cup which forms the principal part of the front. It therefore rests 

 on the periphery of the disc (c, c 1 , c- 3 ), so that a delineation of the one defines the contour 

 of the other. The spiral commences (b 1 ) at the extreme right of the front, and, sweeping 

 around ventrally and just before the edge of the mouth (m) of the vestibule (v), passes 

 to the extreme left, and thence along the dorsal edge of the cup, whence it passes toward 

 its starting-point on the right, but a little exterior to it, so as to overlap it. Thus far it 

 follows the edge of the cyathiform disc, and forms a distinct border throughout its 

 circumference ; but in passing to the termination of its course it runs along the extreme 

 brink of an inclined plane (figs. 11, 12, c 4 ) which rests on a cornice-like projection that 

 extends obliquely across the body, from the right, slightly backwards, toward the left, as 

 far as the aperture (m) of the vestibule, and then rapidly narrows and becomes blended 

 (fig. 13, rf 4 ) with the body beyond. In fact the vestibule (v) is buried for its major part 

 in this oblique projection, and opens at the widest, or terminal part of the inclined plane 

 which forms the anterior face of the hitter. Consequently the vibratory crown, when 

 following the border (d s ) of this plane, passes exterior to, and along the ventral side of the 

 aperture of the vestibule, but, instead of going beyond it, gradually approximates it, and 

 finally entering at its left side, and taking an oblique course toward the right, plunges to 

 its very bottom, in one unbroken, single line (fig. 13, b 2 ). 



In the true Vorticellidaj the disc is a prominently marked organ, and is more or less 

 elevated above the annular peristome; whereas in the Trichodina before us the peristome 

 (d, d\ d 3 , d i , d b ) is not a closed circle, but is blended with the spiral margin of the disc 

 (c, c 1 , c 3 , c 4 ), or rather the disc, instead of projecting beyond the rest of the body, is 

 sunken (c, c 1 ), — invaginated, as it were, — and has a deep cyathiform contour, and its 

 margin is only separated from the peristome (fig. 15, d 1 ) by the slight furrow (b 3 ) in which 

 the cilia (b) of the vibratory crown are implanted. This relationship is strikingly exem- 

 plified in another way ; for when the animal is contracted (fig. 10) and the peristome 

 (d 1 , d 2 ) rolled inwardly, the vibratile row of cilia (b) is not to be found at the bottom of 

 the enclosed space, — as is the case when the like phenomenon occurs in Vorticella, 

 Zoothamnium, Carchesium, and Epistylis, — but hangs down into that space, like a fringed 

 curtain, from the inrolled edge of the peristome. The distinction between disc and peris- 

 tome is therefore no more marked than in Stentor, and, in consequence of the relation 

 of the two, the peristome, instead of traversing the ventral side, and forming a complete 



