82 THF. r.OTIFF.RA. 



suspected, being absolutely cnnccaleJ within tlie rounded outline of the head ; but, at the 

 will of the animal, are suddenly pushed out horizontally, by eversion of the skin, to 

 a length more than half the diameter of the head. They then form oblique cones, 

 which are truncate at their tips ; but the skin there, which seems in some sort double, 

 is at every instant drawn in a little, as if very sensitive. The outer upper corner of each 

 is richly ciliated ; and the ciliary action, at this point of each, makes a strong vortex, into 

 which floating atoms are drawn, and whirled round as in those of the Bdelloids. The 

 auricles are often extruded when the animal is not swimming, but grubbing among the 

 sediment ; and they do not sensibly augment the speed, then ; but if extruded during 

 the swimming, they do so notably. Each can be thrust out in varying degrees; 

 and very often one is out while the other remains concealed : they are manifestly 

 very flexible. No antenna from the occiput is visible ; and the tentacles on the 

 lumbar regions are very minute tubules projecting through the internal skin, and con- 

 nected with a visible basal area on the exterior of a vascular membrane which sur- 

 rounds the abdominal viscera. I can discern, even with a high power, no seta; at the 

 tips of these tubules: but possibly these maybe retractile. Indeed, the tubes them- 

 selves are not always apparent. After death, the ventral surface being in view, a thread 

 was distinctly seen on each side proceeding from the base of the lumbar tentacle, 

 dividing into two branches at about mid-length, and going up to the sides of the brain. 

 Each thread, both before and after the division, had a sensible diameter, and showed 

 a double outline. No imder lip breaks the uniform rotundity of the frontal outline. 

 But, in a ventral view, when it was still and contracted in dying, I have observed an 

 ovate line, as of a minute orifice, just within the edge (fig. 4ii, which may possibly 

 have marked the place where a lip had protruded. 



The general figure of the animal much resembles that of N. aurita ; but is more 

 variable, as if the integument were softer and more flexible. A momentary glance 

 while it was turning left the impression that a segment would be as at fig. 4a ; as if the 

 ventral surface were dilated and flat. The skin was free from gelatinous envelope. 



A stout foot of three joints carries two toes of the blade-form, stout, of uniform 

 width, somewhat long, straight, and pointed. Behind them, separated from them by 

 the cloaca, and from the gibbosity of the trunk by a strong constriction, there is a large 

 bladder-like inflation of the skin, thrown into strong folds or creases, which must be 

 taken to represent the tail. It is colourless, and appears quite empty ; it is constantly 

 changing its outline, but ever falls into the same folds. It is slightly bilobed, and 

 seems somewhat dilatable. This great fat ventricose tail is a conspicuous character, by 

 which this species may in a moment be recognised. The internal economy is, in most 

 examples, sufficiently clear. A three-fold brain is seen : the mid-lobe pear-shaped with 

 a long slender neck, the bulb reaching far below the mastax ; the side-lobes compara- 

 tively short. I have seen the mid-lobe filled with granular matter, not quite opaque, 

 but darkly turbid. A deep-red eye, large, oblong-square or ovate, is seated on the neck 

 of the mid-lobe. An ample mastax, with normal tropbi, nearly fills the breadth of the 

 pectoral region; followed by a vast stomach, in most examples, densely filled with dark- 

 brown conglobate rolls of food ; sometimes with no glands visible, at others with two 

 •small glands, dark, with a large oil-globule within each, of deep orange hue, whose rich 

 refraction of light has a very striking effect, like a pair of coloured carriage-lamps. 

 The ovary often has a great egg, nearly mature. Lateral canals, one on each side, are 

 more or less clearly discerned^ on one of which I have seen one vibratile tag ; but I 

 have not been able to detect a contractile vesicle. 



In manner of lif(^ this, like its congeners, is dull and slothful, rolling stupidly and 

 aimlessly about, and ever altering its form, but not much given to locomotion. Now 

 and then, however, it seeks a new locality ; and then it shoots away in a straight line, 

 •with considerable swiftness and grace, cleaving its path, with dilated front, through the 

 water. I was so fortunate as to be present at the dinner of this species, as I had been at 

 that of C. lahiatus. Several large algw were strewn around, among them a Chisterium, 



