OF THE PROTOZOA. NOCTlLrCIDA. 383 



power of motion." These appearances do not at all convince us of the tubular 

 character of the tentacle ; for they are attributable to the difference of action 

 of the chemical reagents upon the contained matter and upon its investment. 

 Dr. "Webb adds — " I have never perceived any tendency to restoration of the 

 lost part, nor any independent movement in the detached fragment. The 

 stump continues active, and readily comes off at the base. The point is a 

 Uttle flattened. When the animal is killed in such a manner that this organ 

 has free play, it always shows a disposition to coil up spirally." 



Prof. Huxley's comparison of the Noctiluca, in figure, to a peach is very 

 good, and conveys a clear idea of the relative position of the external groove 

 and its appendages {J. M. S. 1854, p. 50). " One surface," he writes, " is a 

 httle excavated ; and a groove or depression runs from one side of the excava- 

 tion, halfway to the other pole. Where the stalk of the peach might be, a 

 fihform tentacle, equal in length to about the diameter of the body, depends 

 from it, and exhibits slow wa\y motions when the creature is in full activity. 

 I have even seen a Noctiluca appear to push repeatedly against obstacles with 

 this tentacle." Behind the tentacle is a rounded or oval mouth, having a 

 harder margin extending from the base of the tentacle, along its right side, in 

 the form of an elevated ridge. This ridge has a horny appearance (although 

 Dr. Webb declares it to be of fibrous consistence), and is usually described as 

 sigmoid in outhne. About its middle is a triple (tricuspid) tooth-like eleva- 

 tion, composed of a middle, bifid, large portion, and a smaller one on each side. 

 Dr. Webb says that when this tooth is " seen in profile, it has the appear- 

 ance of a conical papilla, or, with a slight change in the point of view, of a 

 hooked process terminating in a sharp nib. It readily fields to pressure ; 

 and I have seen it become shrivelled up from the use of astringents, before 

 motion ceased in the cilium and tentacle .... The ridge may be sometimes 

 observed in regular contractile action. Corresponding with these contrac- 

 tions, I have witnessed a to-and-fro motion of the tooth, as though working 

 on an axis in a dii^ection towards the base of the tentacle. A good illustra- 

 tion of this performance is given by bending the fore and middle fingers, and 

 flexing them on the palm of the hand." On the other hand. Prof. Huxley 

 states that he never observed any movement in this tooth-like body. 



The oral aperture opens into a funnel-Hke ca\dty or pharjmx, from the 

 bottom of which a ciliary process extends, having a rapid undulatory move- 

 ment, and retractile. Mr. Huxley only now and then detected this cilium, 

 and states that it is difficult of observation ; but Dr. Webb says — •' The 

 cilium may be found in every instance in which it is looked for with a 

 quarter-inch glass, or even with the half-inch, provided the creatui'e is left 

 at perfect hberty, and is made to move if not in the right position. It often 

 remains at rest for some time, and then from above looks like a small bright 

 spot at the base of the ' tooth ; ' or it may occasionally be seen extended over 

 the S-shaped ridge, or even the base of the tentacle. I have many times 

 detected it in motion from behind, thi^ough the intervening substance of the 

 body, and have noticed it vibrating vigorously long after rupture of the 

 integument and partial discharge of the contents. A Chara-trough, or shallow 

 concave ceU, is most convenient for observations on this part, as the animal 

 swims close to the under surface of the thin glass, and may be made to turn 

 in any direction." 



A minute oval aperture is represented both by Huxley and Webb as open- 

 ing into the funnel-shaped oral cavity. This last expands into an ahmentary 

 space " of very various form and dimensions, capable of great dilatation, and 

 presenting no distinct walls, but rather excavated in the central substance of 

 the body, which is connected with the parietes by numerous granular radi- 



