AND PHYSIOLOGY OF TRICIIODINA. 127 



yellow color, and was finely granulated throughout. In profile, or rather in a foreshort- 

 ened view of its length, it was quite conspicuous, hut where it extended across the vision 

 it was so excessively faint as to nearly escape the eye, even though the utmost care was 

 taken to ascertain its presence and exact position. 



§ 9. Resume. 1 



Reducing, now, the details which have been given in this memoir to the briefest expres- 

 sions, we have the following summary in an aphoristic form. In its healthy, unrestrained 

 condition, Trichodina pcdictdtis is very dissimilar from the hitherto published representations 

 of it. The illustrations of Ehrenberg, Dujardin, Stein, and Busch, represent the animal in 

 an abnormal, more or less reverted attitude, — the result of studying the animal in a confined 

 state, or when in an unhealthy condition. It has a deep, cyathiform, or dice-box shape, 

 with an irregularly and longitudinally furrowed and plicated exterior. There is no disc, or 

 it is represented by the depressed, cupuliform area which is bordered by the vibratory crown. 

 The peristome is not a closed circle, as in Vorticellidje proper, but follows the spiral course 

 of the vibratory crown, and vanishes near the aperture of the vestibule. The vibrator// 

 crown consists of a single row of vibrating cilia, which winds along the margin of the spiral, 

 dexiotropic peristome, just at the edge of the cupuliform disc, and descends thence to the 

 left of the vestibular aperture, and entering it, plunges to the bottom of the vestibule, in 

 an unbroken line. Neither Trichodina nor any of the Vorticellida; possess a vestibular lash 

 or bristle, and the latter is an optical illusion. The posterior truncate end of the body is 

 margined by a well-defined, annular velum, immediately behind which, and arising from the 

 same basis, is a complete circle of vibrating cilia. The so-called adherent organ, or apparatus 

 of hooks and radii, consists, firstly, of a distinct, separable, annular border, whose opposite 

 faces are dissimilarly striated by perfectly straight, transverse ridges ; secondly, of a compli- 

 cated circle of disseverable hooks, which are applied to the posterior face of the striated, 

 annular border, along its proximal edge ; and thirdly, of a series of T-shaped radii which lie, 

 one by one, opposite the several hooks, and converge toward the axis of the basal plane of 

 the body. The vestibule and oesophagus are as well marked, each in its own way, as in any 

 of the Vorticellida?. The vestibule opens near, and posterior to, the cilia-crowned margin 

 of the sunken, cupuliform disc. The anus opens into the vestibule a short distance from its 

 mouth, and on the right side. The contractile vesicle is a simple cavity, which performs 

 its systole once in fifteen seconds. The reproductive organ is a knotted band whose antero- 

 posterior thickness is much greater than at right angles to that ; and it lies, in the form of 

 a crescent, near the base, and transverse to the longitudinal axis of the body. 



The extraordinary and almost incomprehensible position and form of the disc of this 

 singular appendage of the Vorticellidan group seem to render it desirable that no pains 

 should be spared to make the relations of its organs to each other as clear to the under- 

 standing as it is possible to do with the help of figures. The accompanying diagramic 

 illustration of a longitudinal, sectional, or rather profile view of Trichodina pediculus, is par- 

 ticularly intended to exhibit the outline of the sunken, cup-shaped disc (c, c 1 ), and its close 

 connection with the peristome (d 1 , d'") ; but in addition to this it is designed to show, in an 

 outline sketch, the relations of the internal organs to the walls of the body. The con- 

 tractile vesicle (cv), not being strictly in the plane of the section, is represented in dotted 



1 The principal points of this resume are to be found in the Proceedings of the Boston Society of Natural History, Oct. 

 18th, 1SG5. 



