AND PHYSIOLOGY OF TRICHODINA. 129 



Fig. 3. An attitude occasionally, but briefly assumed by healthy specimens. The body is simply shortened, but 

 without changing or reversing the relative positiou of the organs. 200 diam. 



Figs. 4 and 5. Shapes assumed when swimming, different from those already described. 200 diam. 



Fig. 6. An individual with the edge of the cup-shaped front (disc) rolled back so as to expose the bottom of the 

 cup. 200 diam. 



Fig. 7. A partially retracted individual, with one side of the cupuliform front rolled back. 200 diam. 



Fig. 8. A profile view of the left side, showing the following parts, viz : the left flank (c") of the front partially 

 reverted, and the right flank in the distance bearing the vibratory crown (b) ; the bottom (c) of the cupuliform disc 

 iu the distance, and its flank in profile (e 1 ) ; the contractile vesicle (cv). at full diastole, lying near the ventral side of 

 the body; the peristome (d) opposite the mouth (m), i.e., where the cilia — of the vibratory crown (b) — leave it 

 and enter the vestibule (v), also the profile (d 1 ) of the same at the dorsal margin ; the falsely called vestibular lash 

 (bristle) (e) apparently attached near the dorso-anterior side of the vestibule ; the velum in profile (f), and nearer 

 the observer (aty ! ) overhanging the base of the posterior row of cilia (g) ; the ring (h 1 ) of hooks of the adherent 

 organ foreshortened, — i. e., seen strictly edgewise; the left half (n 1 ) of the nucleus most conspicuous next the 

 back, where its length is foreshortened ; the oesophagus (o to o 1 ) partially filled by a nutritive pellet in the process of 

 formation, and rapidly revolved by the action of the vibratile cilia ; the filmy, colorless outer wall (p) projecting 

 very conspicuously in profile, and in marked contrast with the bright amber-colored inner one (p 1 ) ; the general 

 digestive cavity occupied by numerous " digestive vacuoles " (q), nutritive pellets, and smaller alimentary concretions ; 

 the wide aperture (m) of the vestibule (v), and the latter obliquely traversed by the posterior termination of the 

 spiral, vibratory crown. 850 diam. 



Fig. 9. A transversely sectional view of the mid-region of the body, to show its irregular contour, and the corru- 

 gations of the outer (p) and inner (p y ) walls. 850 diam. 



Fig. 10. A dorsal view of an individual whose peristome (d 1 , d~) is inrolled, and with it the vibratory crown (b), 

 which hangs down into the enclosed space about the partially raised, boss-like bottom (c) of the disc. The contractile 

 vesicle (cv) is in partial diastole. The nucleus (n) lies next the back. The principal feature in this figure is the 

 adherent apparatus (i, h, I, l l ), which is copied whilst it is in the act of embracing a highly convex surface, and has 

 therefore an inverted saucer-shaped contour. The radii (i) are iu the extreme distance ; the hooks (h) project in 

 the opposite direction ; the striated membrane shows its breadth in the profile (/), and exhibits its milled edge (I 1 ) 

 and the coarser stria; where it projects toward the observer. The velum (f) is at its fullest expansion, and allows 

 its thickened margin (f 1 ) to be seen very distinctly, where it overlies the gaps between the groups of vibrating cilia 

 (g). The cilia of the basal vibratory crown are represented as they appear sometimes when moving in groups or 

 successive waves, and when they most resemble a torn, undulating membrane. 650 diam. 



Fig. 11. A bird's-eye view of the left side and of the anterior end of the body, partially exposing the depressed 

 face (c*) of the cupuliform disc. The vibratory crown (b) is displayed throughout its length, from its beginning 

 (b l ) on the right side over its spiral sweep by the ventral and dorsal sides, and thence to its downward coil into the 

 mouth (m) of the vestibule. The peristome follows the same course as the vibratory crown, and appears as a 

 distinct rim (d\ d & ) just outside the base of the cilia, until, after descending along the edge (d 3 ) of the inclined 

 plane (c 4 ), it vanishes on the left of the mouth (m). The false vestibular lash (e) or lumen of the vibrating tips of 

 the cilia. The velum (f,/ 1 ), shown very clearly in the profile (f), projecting like a tongue, and undulating inde- 

 pendently of the vibratory cilia (g). The circle (h) of hooks and the striated membrane are drawn but just distinct 

 enough to show their position. The mouth (m) of the vestibule appears as an oval aperture, lying between the 

 first (7/ 5 ) and second (d 3 ) coils of the peristome. The oesophagus (o) is very much expanded at its bottom by a 

 fully formed nutritive pellet, just at the moment when the latter is about to be passed into the digestive cavity. 

 The nucleus (n, n l ) lies fully in view, with its left end («') nearest the observer, and its right half in the distance, 

 beyond the contractile vesicle (cv). 650 diam. 



Fig. 12. A bird's-eye view of the ventral side and front of a slightly retracted individual, exposing the dorsal 

 flank (c 8 ) of the cupuliform disc. The anus (a) appears as a distinct opening (when the fasces are making their 

 exit) at the right side of the vestibule, whose interior is here partially exposed in the full-face view of the gaping 

 mouth (m). The descent of the vibratory crown along the edge (d 3 ) of the inclined plane (c 4 ) is its most note- 

 worthy feature in this view. Its beginning (b 1 ) on the right side of the front is also clearly brought out. The 

 dorsal flank (c 3 ) of the cup-shaped disc presents an unobstructed view, but its bottom (c) is seen in profile through 

 the side of the body. Its extension in the form of the inclined plane (e 4 ) has already been noticed. The contrac- 

 tile vesicle (cv) is represented in partial systole, a very marked feature when contrasted with its derai-diastole 

 (fig. 10, cv). The peristome is particularly noticeable as a distinct border (c/' ! ) along the edge of the inclined plane 

 (c 4 ), and for its disappearance at the left side of the mouth (m). The pseudo-vestibular lash (e) or tips of the 

 vibrating cilia raised above the position which they usually occupy, and in the attitude assumed during the expulsion 



ME MOIRS BOST. SOC. NAT. HIST. Vol I. 33 



