120 H. JAMES-CLARK ON THE ANATOMY ■ 



ring, as in the true Vorticellidae, descends, with the vibratile organ, to the mouth of the 

 vestibule, and then vanishes in the general surface of the body. 



The vibratile cilia (b) of this organ are very long and slender, thread-like bodies which 

 stand in close rank, in a single row. They arise from the bottom of a slight furrow 

 (fig. 15, b z ) which extends along the inner side of the peristome (d 1 ), from its beginning 

 (b 1 ) on the right, throughout its first turn (<7 5 ), and thence to its termination (d) at the left 

 margin of the aperture of the vestibule. They usually incline in the direction which leads 

 toward the mouth, and along the margin of the disc, — i. e., throughout the extent of the 

 first turn of the spiral, — and they at the same time spread outwardly as if in continuation 

 of the flare of the cup ; but occasionally they incline toward the centre of the depressed 

 disc, and produce a vortex therein by their combined action. 



The oesophageal cilia. The vibratile cilia which line the oesophagus [o, o 1 ) and seem to be 

 continuous with those of the vibratory crown (b) which enter the vestibule, are much 

 more delicate and shorter than they, and although they perform an analogous duty in the 

 preparation of the food before it is finally taken into the general cavity of the body, yet, 

 inasmuch as they are occupied in the more special office of moulding the intussuscepted 

 matter into nutritive pellets, they in all probability are to be looked upon as belonging 

 to a separate system from those of the vibratory organ. 



The so-called bridle of the vestibule of Vorticellidae, which was first described as such by 

 Lachman (Mull. Archiv. 1856, s. 348, Taf. XIII. figs. 1-5, eg), is an optical illusion! It was 

 almost by accident that we were induced to doubt the character of this seemingly definite 

 body. After having successfully followed two rows of cilia from the stem of the rotatory' 

 organ into, and to the very bottom of the vestibide of an Epistylis (E. galea Ehr.?), it seemed 

 very strange that the "bristle of Lachman" had not been met with, during such a close 

 and searching scrutiny. Recalling its position, as described by Lachman and by Claparede, 

 and as we thought we had seen it on former occasions, it was observed, that, whilst one of 

 the rows of cilia, which had just been traced into the vestibule, occupied its right side, 

 the other row was in the position of the so-called bristle ; i. e., it trended along the left 

 side of the vestibule. Occasionally it was noticed that both the right and left rows of 

 cilia had the appearance of single vibratory lashes, and that the left row, where it ran out 

 beyond the aperture of the vestibule, and thence upon the stem of the rotatory organ, had 

 a particularly strong resemblance to a single lash or bristle ; especially when the cilia 

 projected toward the eye, so as to foreshorten the whole row. In the latter case it is 

 easy to see how, when the cilia vibrated in regular succession, they would produce the 

 effect of an undulating line. The closest scrutiny, with a Tolles one-eighth of an inch objec- 

 tive and a B ocular, — equalling a magnifying power of 750 diameters, — utterly failed to 

 discover the least trace of anything else which might correspond to the so-called vestibular 

 bristle ; and it was therefore fully determined upon that there is no such body existing in 

 the vestibule of the Epistylis. The same observations were also made upon another 

 species of Epistylis (E. grandis Ehr. ?), and upon Carchesium (C. polypinum Ehr. J, and 

 Vorticella (V. nebulifera Ehr.), and with the same result. 



Notwithstanding this forewarning, it was very difficult to dispel the illusion when the 

 vestibular cilia of Trichodina were under investigation. If one observes attentively, how- 

 ever, it will be noticed in the first place that what appears to be a single cilium or bristle 

 never projects beyond the tips of the cilia which lie outside of the aperture of the 

 vestibule ; and secondly, that when the tips of these cilia are followed along with the eye ? 



