2C2 



MUSEUM OF ANIMATED NATURE. 



[Gladcos. 



•eWe* by means of the edge of their mantle, and by 

 their tentacle*, which terve a> oan. . 



A» example* of ihi* eroup we may mention Don*. 

 Polyeera. Tethy». I-anio)jerii», &c. Of the general 

 a»pect ol these raolliwk*, commonly called »ea-»lug8, 

 our pictorial upecimen* will convey a clear idea. 



2635.— The Hob-nki) Dobw 



(Dorii cormula). Polyeera comiila. CuV. 



The iubgenera upon which the genus Dons, a 

 term originally applied by Unnieus to a single 

 specie*, is subdivided, are several, depending upon 

 minor peculiarities. , ^ • ^ .u 



In the present species (Polyeera of Cuvier), the 

 branchiie, in the form of projcctine foliated branches, 

 are disposed as usual in a circle, at the posterior 

 part of the body, and followed by two membranous 

 llrips which cover them when danger threatens. 

 The anterior edge of the mantle projects in the form 

 of strnp-like proloneations symmetrically disposed. 

 Referring to Fig. 2t»'>, a represents the animal as 

 seen from above ; 6, as seen from below ; c, a side 

 »iew. 



2636.— Tub Flat Dobis 

 (Doris Soled). In this form the body is extremely 

 depressed, the anterior border of the mantle is 

 simple, and the branchise assume the shape of a 

 foliated star at the posterior part of the body. 



2637. — The Jagged Dobis 

 (Dorit laeera). In this form the body is convex 

 above, with tuberculous eminences, club-like ten- 

 tacles, and (he branchiae in a circle of tufts at the 

 posterior part of the body. 



2638. — Leach's Doris 

 (Onchldoris Leachii). It is only on certain 

 anatomical points that this genus is separated from 

 Doris. The tentacula are four, besides labial ap- 

 pendages : a, side view of the mollusk; b, under- 

 neath view. 



2639. — ^The Pekonia 



{Peronia Mauritiana). A slug-like mollusk, with 

 the branchisB nearl;; retiform in a cavity situated i 

 at the posterior region of the back; and opening 

 externally by a round mesial orifice pierced at the 

 inferior and posterior part of the borders of the 

 mantle. M. Blainville observes that this genus 

 ■contains the marine onchidia of Cuvier. of which 

 four or tive species are known from the southern 

 hemisphere. fluvier, we may add, regards the 

 onchidia (genus onchiJium) as forming part of the 

 pulmoniferous gastropods; but M. de Blainville 

 refers the genus to the same family as that contain- 

 ing the Doris. Cuvier, commenting on this view 

 of De Blainville, says, " I cannot perceive any 

 real difference between the respiratory organ of 

 Onchidium, or Peronia, and that of the other 

 pulmoniferous moUusks." a, side view of Peronia ; 

 b, the under surface or foot. 



2640.— The Ptebosoma. 



(Pterosotnd). M. Lesson established the genus 

 Pterosoma on a single species of mollusk which he 

 discovered in great abundance in the equatorial 

 seas between the Moluccas and New Guinea, where 

 it was seen swimming about with great celerity. 

 The animal is gelatinous, transparent, elongated, 

 cylindrical and convex in the middle : the body lies 

 between two lateral swimming membranes, one on 

 each side ; these are delicate and horizontal, 

 originating at the tail and continuing in an oval 

 form beyond the head, where they unite in front of 

 the mouth ; the anterior border is thicker than the 

 posterior, which is narrowed and thin ; the mouth is 

 simple, there are no tentacles, the eyes are sessile, 

 ubiong, and approximated to each other. So trans- 

 parent is the body that the internal viscera may be 

 seen through its substance. The branchi» do not 

 appear to have been detected, but it is not impro- 

 bable that the swimming membranes may serve the 

 purpose of those aerating organs. 



2641. — The Laniogebus 



{Laniogerus El/ortii, Blainville). This animal is 

 closely allied to the Glaucus, and the genus was 

 established by M. de Blainville on an individual in 

 the British Museum. M. Rang remarks that its 

 figure recalls the appearance of Glauci preserved 

 in spirits of wine, which, having become swollen, as 

 is usually the case after death, have also at the 

 same time lost some of their branchial cirrhi. 

 There are two pairs of tentacles ; the head is dis- 

 tinct, the mouth subterminal ; on each side of the 

 body are the branchise, forming a series of soft 

 laminee finely pectinated. Referring to Fig. 2641, 

 a represents the mouth ; b, the branchial cirrhi. 



2642.— The Glalccs 



(Oiaucua hezapterygitu). This brilliant sea-slug, 

 common in the Mediterranean and extensive^ 



spread through the wide ocean, is distinguished for 

 tne beauty of its colours, azure blue and silvery 

 white being the predominating lints. It swims in a 

 reversed position with great quickness. The general 

 characters are as follow :— Texture gelatinous, form 

 elongated, slightly flattened, and terminating in a 

 point ; foot very narrow and almost rudimentary ; 

 nead distinct, furnished with four very short flattened 

 and triangular tentacles, mouth subterminal ; 

 branchite disposed in pairs on the sides and fitted 

 for swimming, consisting of oblong processes sur- 

 rounded by digitated appendages. The species, 

 says Cuvier, are not as yet well distinguished. 



M. Deshayes in his edition (1836) of Lamarck 

 remarks that, notwithstanding the researches of 

 several accomplished naturalists, there still exists 

 great uncertainty with respect to many points in 

 the anatomy of this genus. The description of M. 

 de Blainville, he observes, leaves doubts concerning 

 the organs of respiration ; nor is it, he adds, certain 

 that the digitations of the fins are branchise ; indeed 

 he is inclined to believe"that they are not; and he 

 quotes the observations of M. Quoy, who affirms 

 that these digitations are very caducous in the 

 living animal, which detaches them when they are 

 touched ; and he argues that it is scarcely credible 

 that this would take place were these parts actually 

 destined for so important a function as that of 

 respiration. M. Deshayes therefore insists upon the 

 necessity of new researches upon the organization 

 of these curious animals. He considers, moreover, 

 that one species only is as yet known, of which most 

 of the figures published are very inexact, with the 

 exception of that given by MM. Quoy and Gaimard 

 ('Voy. de I'Astrol. Zool.,' t. 2, pt. 26), which, he 

 says, conveys a good idea of this elegant mollusk. 



The following account of a species of Glaucus, by 

 Mr. J. C. Lees, was read at one of the scientific 

 meetings of the Zool. Soc, accompanied by a draw- 

 ing of the animal referred to : — 



" Being at sea about two years ago, between the 

 Azores and the Bahama Islands, in about lat. 30^ N., 

 long. 50° W., I observed the surface of the sea 

 thickly covered in every direction, as far as I could 

 see. with small animals. Having drawn up some of 

 them in a bucket, I found them to have bodies and 

 tails nearly resembling those of a lizard, but the 

 head was thick and blunt, without any appearance 

 of a neck. I could not discover either eyes or mouth. 

 Four short arms or limbs were attached to the body, 

 nearly in the same situation as the legs of a lizard, 

 and from the outer end of each of them proceeded 

 in a radiating direction fifteen slender feelers, 

 diminishing to a fine point, the centre ones larger 

 than the others. The animals were of a deep but 

 vivid blue colour, with a bright well-defined line of 

 silver down the back from the head to the extremity 

 of the tail ; this sireak fif silver branched off also 

 into the arms and along each of the feelers, till 

 towards the points it formed so thin a line as to 

 become gradually imperceptible. The under part 

 of the animals was of a silvery white ; their appear- 

 ance was very beautiful : they were about one inch 

 and a half long from the front of the head to the 

 end of the tail, and about the same across, from the 

 extremities of the longest of the opposite feelers. 

 The water continued covered with them for two 

 days, during which time we sailed over about one 

 hundred miles ; the number of them must, therefore, 

 have been prodigious. They remained perfectly 

 quiet on the water, except when touched, when they 

 either partially or entirely drew themselves up into 

 a ball. They could in this manner draw up either 

 one or more feelers, or the whole limb with its 

 fifteen. They did not appear to notice the approach 

 of a finger or piece of stick until it actually touched 

 them, and then did not attempt to swim away, but 

 only drew up the part touched with a sudden and 

 apparently angry jerk of the head. If the touch was 

 violent or repeated, they drew themselves entirely 

 up in a globular form, and the same thing occurred 

 wrien they came in contact with each other. I 

 endeavoured to preserve some of them alive by 

 keeping them in sea-water, but in three or four days 

 they all died, and immediately shrunk up into a 

 shapeless mass of a brown colour. I was equally 

 unsuccessful in my endeavour to preserve them in 

 spirits, in strong salt and water, or in vinegar ; the 

 instant they were introduced into those liquids they 

 shrivelled up into a browinish shapeless mass." 

 (' Proceeds. Zool. Soc.,' April 23, 1833.) 



In the 'Proceeds. Zool. Soc' for 1836, p. 113 et 

 seq., is the following interesting paper on the 

 Glaucus by Mr. G. Bennett, detailing the results of 

 his personal observations : — 



"On the 20th of April, 1835, during a voyage 

 from England to Sydney, New South Wales, in 

 latitude 4" 26' N., and longitude 19° 30' W., with 

 light airs and calms prevailing at the time, about 

 3 p. M., a number of damaged and perfect specimens 

 of the Glaucus hexapterygius, Cuvier, were caught 

 in the towing net. On being immediately removed 

 fVom the net and placed in a glass of sea-water. 



they resumed their vital actions and floated about 

 in the liquid element, exhibiting a brillianiy of 

 colour and peculiarity of form which did not fail to 

 excite the admiration of the beholders. 



"The back of the animal, as well as the upper 

 surface of the fins and digitated processes, and the 

 upper poition of the head and tail, was of a vivid 

 purple colour, varying occasionly in its intensity ; 

 appearing brighter in colour when the animal was 

 active or excited, and deeper when remaining 

 floating tranquilly upon the surface of the water. 

 The abdomen, and under surface of the fins, are of 

 a, beautiful pearly white colour, appearing as if it 

 had been enamelled. The usual length of my 

 specimens, measured from the extremity of the 

 head to the tail, when extended floating upon the 

 surface of the water, was If inches; sometimes one 

 or two lines more or less. The body of the animal 

 is subcylindrical, terminating in a tail, which ara- 

 dually becomes more slender towards the extremity, 

 until it finally terminates in a delicate point. The 

 head is short, with very small conical tentacula in 

 pairs ; two superior, and two inferior ; three (and in 

 G. octopterygius, Cuvier, four) branchial fins on 

 each side, opposite, palmated, and digitated at their 

 extremities; the number of digitations, however, 

 varying; and the centre digitations are the longest; 

 the first branchial fins, those nearest the head, are 

 larger and denser than the others. The mouth is 

 armed with bony jaws ; the body is gelatinous, and 

 covered by a thin and extremely sensible membrane. 

 "These little animals were very delicate and 

 fragile in their structure, and although many, 

 indeed I may say numbers, were caught, yet very 

 few in comparison were found to be in a perfect 

 condition, some being deficient in one, two, or more 

 fins, and others being completely crushed. Not 

 one of the specimens caught on this occasion, or 

 during the voyage, had the silvery line or streak 

 running down the back, from the head to the ex- 

 tremity of the tail ; branching off also to the fins 

 and along the centre of each of the digitations. 

 Several Porpitae were also captured in the net at 

 the same time with these animals, and serve as food 

 for them. 



" It caused much regret to see the change death 

 produced in the beauty of these interesting little 

 animals, and all means of preserving them were 

 found to be useless. When placed in spirits, the 

 digits of the branchial fins speedily became re- 

 tracted, the beautiful purple gradually faded and at 

 last disappeared, and the delicate pearly white of 

 the under surface of the body and fins peeled off 

 and disappeared ; thus did this beautiful mollusk 

 become decomposed in less than the space of an 

 hour. Some moDusks quickly lose their colour 

 after death, but retain their form lor a long time; 

 but these speedily change after death both in form 

 and colour, and the beauty before so much admired 

 perishes never to be regained. 



" When taken in the hand, the under surface of 

 the animal soon becomes denuded of the beautiful 

 pearly white it previously had, and at that time 

 appears like a small transparent bladder, in which 

 a number of air-bubbles are observed, together with 

 the viscera. On the abdomen being laid open, a 

 large quantity of air-bubbles escaped ; and perhaps 

 a query may arise how far they assist the animal in 

 floating upon the surface of the water? 



" The figure of Glaucus hexapterygius in Cuvier's 

 work ' Sur les Mollusques,' is tolerably well executed, 

 but no engraving can convey to the beholder the 

 inconceivable delicacy and beauty of this mollusk ; 

 in the engraving alluded to there is an inaccuracy, 

 at least as compared with the specimens before 

 nie, — in the digitated processes of the fins not 

 being sufficiently united at the base ; in the living 

 specimens before me they were united together 

 at the base, and then branching off became gm- 

 dually smaller until they terminated in a fine 

 point. 



" But few of these animals were caught after the 

 20lh until the 24th of the same month, in latitude 

 2" 26' N., longitude 19= 51' W., when, having light 

 airs from S. by E., nearly calm in the morning, a 

 great number were seen floating by the ship, and it 

 was not difficult, by aid of my lowing net, to cap- 

 ture as many as 1 required, lor they swam very 

 superficially upon the water. The whole of those 

 taken proved to be of the same species (G. hexap- 

 terygius) as those before caught. I again placed 

 several of the specimens in a glass of sea-water; 

 they were full of life, sometimes moving about, not 

 very briskly, however,- — and at other times remain- 

 ing floating upon the surface of the water, merely 

 gently moving the fins. As they floated upon the 

 surface of the water in the glass, the sides of the 

 head, back, tail, fins, &c., exjiibited at the time a 

 light silvery blue colour, which was admirably 

 contrasted with the deeper blue of the upper sur- 

 face, and falling into the elegant pearly or silvery 

 white of the under surface of the animal, display- 

 ing an exceedingly rich and eleeant appearance. 



