124 



II. JAMES-CLARK ON THE ANATOMY 



position with the point of contact of the bases of two successive hooks, and at the broadest 

 part protrudes sideways between the latter. The tip of the nail-head projects between the 

 point (i i ) of the succeeding nail and the base (Ji 3 ) of a hook ; the two latter constituting a 

 sort of socket in which the former appears to slide. Tins would seem to show conclusively 

 that this complicated ring may be enlarged or diminished at the will of the animal. 



The faint radiating ridges (i) which occupy the central two thirds of the adherent 

 apparatus are attached one by one to the point (7 4 ) of the nail-shaped bod} r just men- 

 tioned, and at right angles to it. The basal third of these radii is easily seen with a 

 one-fourth inch objective, but even a one-eighth does not distinctly trace the pointed end 

 to the centre of this apparatus. Each radius (i) and the nail-shaped body (Y 1 , r) seem to 

 form a solid piece, a sort of Greek T whose angle is occupied by a faint membrane, or web 

 (i 3 ), which extends from one third to one half the way along tbe nail, and nearly, or alto- 

 gether to the end of the tapering radius. This faint membrane appears to fill the whole 

 space between the radii, in healthy animals. 



In djnng specimens the adherent organ readily separates from the body, en masse; but 

 shortly afterwards the striated membrane loosens from the circle of hooks; and in a brief 

 space of time the latter becomes disjointed, and each hook detaches from its fellow, but 

 remains for a longer period in conjunction with its corresponding radius and nail-shaped 

 piece. 1 



§ 6. The Digestive System. 



This infusorian takes so readily to an indigo diet that the process of collecting food 



1 Various opinions — and all of them at variance with the 

 one promulgated in this paper — have been expressed in re- 

 gard to the nature of the adherent apparatus, and jts motory 

 appendages, the vibratile row of cilia. Siebold (Zeilsch. fur 

 Wissenschajl Zoiil. Bd. II. s. 367), as the following translation 

 shows, has mistaken the row of vibratile cilia (//) for an undu- 

 lating membrane, and has entirely overlooked the velum (/"). 

 He says, " Among the Infusoria, the genus Trichodina is en- 

 dowed with a distinct, undulating membrane, which, applied to 

 the lower margin of the body, in the form of a circle, adheres to, 

 and is supported by, a solid, toothed apparatus, not unlike a 

 watch-wheel. In Trichodina pediculus this vibrating border is 

 entire-margined ; in T. mitra .... the free border of this 

 appears to be deeply and delicately fringed. Trembley, 

 Gceze, O. F. Muller, Carus, Du.jaudin, and others, 

 have, in consequence of an optical illusion, considered this 

 undulating membrane in T. pediculus as a vibrating-cilia- 

 crown." 



Stein (Infusionsthiere, 1854, s. 17G) controverts the asser- 

 tion of Siebold, and insists that the " undulating membrane" 

 of the latter is a crown of cilia ; but yet, as in Siebold's case, 

 the velum has entirely escaped his notice. He writes as fol- 

 lows : " The posterior cilia-crown . . . on account of the very 

 closely set cilia, does certainly readily produce the impression 

 of an undulating membrane margining the rear-body, which not 

 only in T. mitra, but also in T. pediculus, appears to be den- 

 ticulately notched : but let one kill the animal with diluted acetic 

 acid or alcohol, and he will separate each single cilium 

 sharply. That the posterior cilia-crown is connected neither 

 with the toothed horn-ring, nor with the annnliform membrane, 

 let one convince himself thereof by crushing the animal, by 



which one easily separates the entire adherent apparatus, in all 

 its integrity, from tin- body." 



Next Busch {Milll. Archiv. 1855, s. 358) appears in the 

 field of controversy, and, commenting upon the observations of 

 the two foregoing authors, compromises their views by uniting 

 tin' vibratile cilia to the edge of the undulating membrane. 

 This idea is set forth in the following words: " On the so- 

 called hind-body is found the — by Stein first very correctly de- 

 scribed — saucer-shaped rim, on whose base is fastened the ring 

 of the rigid baton-crown, from which the hooks arise. On the 

 foundation of and exterior to, the saucer-shaped membrane is 

 implanted the chief locomotive organ of the animal, the pos- 

 terior cilia-crown. Siebold has explained this as an undu- 

 lating membrane, whilst Stein' has evidently recognized the 

 separate cilia of the same, and only speaks of a cilia-crown. 

 The truth seems to me to lie intermediate, for though I clearly 

 observed the single cilia, especially in dying animals, yet I could 

 never follow them to the margin of the saucer, unless a fissure 

 was present. This organ consists, then, of a membranous un- 

 dulating border, on whose free edge vibratile cilia are inserted. 

 One may convince himself best of this on dying animals, where 

 one sees the gentle pulsations of the border and the cilia." 

 Although it is certain that Busch did not see the velum, as 

 such, and in its proper relations, yet it is not equally clear 

 that he did not have it in view, but confounded it with the 

 row of vibratile cilia which underlie it. 



Finally, as the latest investigator, Claparede (Etudes sur 

 les Infusoires el les Rhizopodes, Memoires de Vlnstitut Gene- 

 mis, 1858-59, p. 130) sustains the view of Stein, demurs to 

 the opinions of Siebold and Busch, and says nothing about the 

 true velum. 



