Tethys.] 



MUSEUM OF ANIMATED NATURE. 



203 



Often, when at rest, the animal would drop one or 

 more of the fins, but on touching them they would 

 be immediately raised to the former position, and 

 that organ was turned back as if to throw otf the 

 offending object, followed at the same time by a 

 general movement of the whole body. On touch- 

 ing the animal upon the back, it eeemed to display 

 more sensitiveness in that than in any other part of 

 the body, judging from the effects produced, in 

 comparison with similar experiments on other por- 

 tions of the body; for instance, the centre of the 

 back was touched lightly and rapidly with a. feather : 

 which caused the little creature to sink as if under 

 the pressure of the touch, throwing at the same 

 time the head, tail, and all the fins upwards, 

 followed by a general distortion of the whole body 

 of the animal, as if the gentle touch had been pro- 

 ductive of severe pain. I invariably found every 

 part of the upper surface of the body very sensitive 

 when touched, and displayed a general movement 

 of uneasiness throughout the whole of the body of 

 the creature. 



"These creatures have a peculiar manner of 

 throwing the head towards the tail, and flouncing 

 the tail towards the head, when they are desirous 

 of removing any object of annoyance. It is at that 

 time these animals seem to recover from their 

 torpidity, and evince the greatest activity in their 

 movements. When much annoyed, they throw the 

 body about with great activity, coiling up the head, 

 tail, fins, &c., in a somewhat rotundilbrm position ; 

 and if the tormenting object is not removed, dash 

 out again in full activity of body, then return to the 

 rotundilbrm position, and there remain for a short 

 period apparently exhausted by their efforts. But 

 on the cessation of the irritating cause, the animal 

 quietly resumed its original position, perhaps 

 dropping one or two of its wearied fins according 

 as its own sensations of ease or comfort might 

 dictate. 



" When nothing irritated this tender moUusk, it 

 ■would remain tranquilly floating upon the surface 

 of the water with scarcely any movement but that 

 which proceeded from the undulating movements 

 of the digitated extremities of the fins, as well as 

 an occasional slight twisting motion of the same 

 organs. 



" I felt much interest in the beautiful display of 

 a circulating fluid on the dorsal surface of these 

 animals, which was afforded me by the assistance 

 of a microscope. Through the semi-transparent 

 membrane of the back, a fluid could be readily 

 perceived close to the surface, evidently flowing 

 m two directions, one taking a course downwards, 

 and the other returning upwards ; but I was unable 

 to distinguish two distinct vessels for these sepaiate 

 actions. 



"These animals seemed to be very torpid in 

 their movements, although sometimes, when float- 

 ing upon the water, they would be seen busily 

 engaged in moving their fins about; but those 

 actions were soon suspended, and their fins were 

 suffered to hang lazily down, as if fatigued with 

 the short exertion, which did not move them one I 

 inch about the glass of water ; and even when the 

 little indolent creatures did take the trouble to 

 move themselves from one side of the glass to the 

 other, it was eff'ected by a tardy motion, stirring 

 themselves first with one fin and then with the 

 other, according as circumstances might require. 



" I placed some small specimens of Porpita in 

 the glass of water containing the Glauci, to observe 

 it they would attack them : for some time one of the 

 Glauci was close to a Porpita, and was even annoyed 

 by the tentacula of the latter touching its back, 

 yet the Glaucus bore this, although with the usual 

 characters of impatience, yet without attempting to 

 attack it. At last it seized the Porpita between its 

 jaws, and by aid of a powerful lens, an excellent 

 opportunity was afforded me of closely watching 

 the devouring process, which was effected by an 

 apparently sucking motion ; and at this time all the 

 digitated processes of the fins were floating about, 

 as at other times when the animal was at rest ; but 

 I did not observe, in one single instance, that they 

 were of any use to the animal, either to aid in the 

 capture or to securely hold their prey when in the 

 act of being devoured ; for the animal seems to 

 depend merely upon the mouth in capturing its 

 prey, as in this and other instances, which I had 

 opportunities of observing, they seized their prey 

 instantly with the mouth, and held it by that power 

 alone, whilst by a kind of sucking motion the prey 

 was devoured. The digitations may therefore only 

 be regarded as appendages to the fins to aid the 

 animal perhaps m the direction of its movements, 

 as it was observed that they turned and twisted 

 them about during the progressive motion (that is, 

 when this tardy animal is pleased to progress, which 

 appeared to me very rarely to meet with its inclina- 

 tion), as if in some way or other to direct the move- 

 ments of the animal. 

 "The Glaucus, after eating the tentacles and 

 Vol II. 



nearly the whole of the soft under surface of its 

 prey, lelt the horny portion, and remained tran- 

 quilly reposing upon the surface of the water after 

 its meal, the only motion visible in the animal 

 being the playing of the digits of its fins. The 

 mutilated remains of the Porpita sank to the bottom 

 of the glass. 



" Soon after, another Glaucus began a devouring 

 attack upon another Porpita which had been placed 

 in the glass, eating a little of it, and then ceasing 

 after a short meal, occasionally renewing the attack 

 at short intervals. On examining the Porpita, 

 which had been partially devoured by the ravenous 

 Glaucus, I found the disc had been cleared of the 

 tentacles and other soft parts ; a small part of the 

 fleshy portion only remaining upon the disc. Only 

 one part of the horny disc exhibited any injury, and 

 that appeared to be the place where the animal was 

 first grasped by the Glaucus. 



" When any of these animals came in contact 

 with another in the glass, they did not display any 

 annoyance, nor coil themselves up, nor did they 

 evince any savage propensities one towards the 

 other ; and they would often float about, having 

 their digitated processes in contact one with the 

 other, without exhibiting any signs of annoyance ; 

 even when placed or pushed one against the other, 

 they did not manifest any irritation, but remained 

 jj undisturbed as in their usual moments of quiet 

 repose. 



"On the back of the animal being seen in a strong 

 light, a black line could be discerned on each 

 margin, and passing down the centre of each fin, 

 and sometimes varied in having two black lines on 

 the upper part of one fin, although the opposite fin 

 may display but one. 



" The margin between the falling of the purple 

 colour of the back into the silvery white of the 

 abdomen often exhibited beautiful tints of a golden 

 green ; but these variations were probably produced 

 by the effect of different rays of light. 



" These animals soon perished ; I could not pre- 

 serve them for any length of time in the glass of 

 sea water, although the water was changed as often 

 as it was thought necessary ; the digitated pro- 

 cesses of the fins were observed to shrink up on the 

 death of the animal, and the process of decomposi- 

 tion rapidly took place, the whole body becoming a 

 shapeless mass, having a bluish colour of deadly 

 hue for a short period, and then became of a black- 

 ish or brownish black colour. I have seldom seen 

 a gelatinous animal which appeared so firm whilst 

 in the water, that proved so speedily to decompose 

 when removed from it ; even the beautiful purple 

 of the back, the silvery or enamel of the abdomen, 

 and the silvery blue of the sides, all speedily vanish, 

 indeed instantly disappear, upon the death of the 

 animal, as if it had been washed off; the expansive, 

 delicate, and beautiful fins and digitated processes 

 are no longer seen ; they shrank up to nothing. 



" Even on taking the animal alive out of the 

 water and placing it upon the hand, that instant 

 almost, from its extreme delicacy, it was destroyed : 

 the digitations of the fins fell oft', the least move- 

 ment destroyed the beauty of the animal : it speedily 

 lost all the deep purple and silvery enamelled tints, 

 and became a loathsome mass. Thus do we too 

 often find animals beautiful in external adornments, 

 curious in their habits and organization, and cal- 

 culated in every respect to supply us with inex- 

 haustible sources of intellectual gratification, doomed 

 speedily to perish ; brief is the period allotted to 

 them in the busy theatre of animated existence ; 

 but doubtless, with the gift of existence, they have 

 received from the bounteous hand of their Creator 

 the means of enjoying their fleeting lives. 



"To place these little animals in the glass of 

 water from the towing net without injury to their 

 delicate structure required care ; so that as soon as 

 they were captured in the net, attached to the 

 meshes, they were not handled, but carefully washed 

 off, which was effected by dipping the meshes in 

 the glass of water, when the animal soon detached 

 itself without sustaining any injury, and floated in 

 the water. 



" Although these animals are so fragile, so easily 

 destroyed on being taken out of their natural ele- 

 ment, yet they fling themselves about in the 

 water without sustaining any injury, without even 

 the loss of any of the digitated processes of the fins : 

 yet when there is much movement of the water in 

 carrying the glass from one place to another, they 

 are evidently disturbed and restless, and the fins are 

 dropped ; if, therefore, a slight motion of the water 

 disturbs them, what can become of these delicate mol- 

 lusks during tempestuous weather; can they be simi- 

 lar to the delicate ephemeris, doomed to live merely 

 tor the space of a day and perish in myriads ? From 

 the immense number seen only from the ship — and 

 how many myriads more extended beyond our range 

 of vision— it conveyed to the mind some idea of the 

 profusion of living beings inhabiting the wide ex- | 

 panse of ocean, and a feeling of astonishment at 



the inconceivable variety of forms and construc- 

 tions to which animation has been imparted by 

 creative power. 



" The tail of this animal has been described as 

 resembling that of a lizard : the comparison is 

 good, not only with regard fo form, but also, with 

 perhaps a little more flexibility of motion, when in 

 action. Sometimes the animal throws its fail up to 

 the body, as if intended to brush off any annoying 

 object, and at other times it has been observed to 

 turn the head towards the side as if for a similar 

 purpose. It seems, in the action of eating, to re- 

 semble a caterpillar 



"No more of these animals were seen until the 

 15th of May at 10 p.m. when in lat. 24° 18-5, long. 

 31° O'-Ol W., moderate breezes and fine weather, a 

 number of Glauci were captured as well as Porpitse ; 

 some of the latter had been partially devoured, and 

 in some only the homy disc remained ; this there 

 was no doubt, from the previous knowledge of the 

 carnivorous propensities of the Glaucus, was theii- 

 work, more especially as we had positive proof that 

 tribes of them were wandering or prowling about 

 the ocean to-night. This was the last time during^ 

 the voyage the Glauci were captured. 



" From these animals devouring the Porpitse, we 

 had positive evidence of their carnivorous habits, 

 independent of the structure of the jaws; and the 

 tentacula of the Porpitse were no protection against 

 their enemies ; indeed these appendages were first 

 devoured and the horny disc was alone left, in many 

 instances being picked quite clean ; from this cir- 

 cumstance we may infer that the horny disc of 

 the Porpitse and Velella;, which previously, and for 

 the last four days, were found in the net, were the 

 remains of those which had been devoured by the 

 Glauci or similar carnivorous mollusks, among which 

 we may with safety include (from the structure of 

 its jaws, and from often capturing it attached to 

 Velella) the inhabitant of the Janthina fragilis or 

 violet shell. 



"The more we pursue the investigation of the 

 actions of living objects, the more we see of the 

 unbounded resources of creative power; and, after 

 all our reasoning, must conclude that some wise 

 purpose, though dimly perceptible to our imperfect 

 understandings, is no doubt answered by this great 

 law of organic formation, — the law of variety." 



Referring to Fig. -2642, a and h are two tubercular- 

 orifices ; c, one of the digitations magnified. 



2643. — Cuviek's Eolidia 



(Eolidia Cuvieri). C'uvier describes the Eolidise as^ 

 having the form of little slugs, with four tentacles 

 above, and two at the sides of the mouth. Their 

 branchiae are laminae or foliations disposed like 

 scales in more or less close array, down each side of 

 the back. They are widely spread through the 

 ocean. According to M. Rang, they do not swira^ 

 but suspend themselves at the surface of the water 

 with the foot uppermost, and move well by means 

 of sudden undulations. 



Cuvier's Eolidia, the figure of which is magnified, 

 is found in the European seas. 



2644. — ^The Cavoi-ixa 



{Cavolina peregrina). The Cavolina has the ten- 

 tacles as in Eolidia, and the branchioe in the form of 

 filaments placed in transverse rows on the back. The 

 Cavolina peregrina is found in the Mediterranean, 

 but other species exist, some of which are very 

 small, as that brought home by MM. Quoy and 

 Gaimard (' Voy. of the Uranie '). 



2645. — The Tekgipes 



(Tergipes lacinulata). With the general form of 

 Eolidia, there are in Tergipes only two tentacles ; 

 and along each side of the back is a row of bran- 

 chiae of a club-like form, each terminating, according 

 to Cuvier, in a little sucker, and serving as feet, by 

 means of which the animal can crawl in a reversed 

 position. M. Rang doubts the existence of these 

 sucking discs. Tlie figures are magnified : a, seen 

 from above ; b, from below. 



2646.— The Tethys 



(Tethi/s leporitm). In the genus Tethys the bran- 

 chiae consist of two dorsal rows of branched tufts 

 unequal alternately from right to left, and from 

 front to rear : the head is rlistinet, and furnished 

 with a large membranous distinct veil, fringed along 

 the edge, forming a sort of funnel, and leading to 

 the mouth, which terminates a short proboscis. The 

 tentacles are two in number, situated at the base of 

 the veil. 



The Tethys leporina, which appears to be identical 

 with the Tethys Fimbria, is a native of the Medi- 

 terranean, living far from the shore, on banks of 

 madrepore, or among floating masses of sea-weed. 

 It uses the veil or membranous expansion of the 

 head as a swimming organ. Its colour is grey 

 spotted with white. Referring to Fig. 2646 ; a ex- 

 ^ 2 D 2 . . 



