its life, either in the water by means of branchia, or in the air by means of lungs. This conclusion rested upon that solid basis which has given such value-a value daily becoming more appreciated-to the views of this great zoologist, his personal observations made on the osteology and splanchnology of the animal. Dr. Garden had, in his correspondence with Linnæus and Ellis, come to the same conclusion from other evidence. Dr. Garden had observed the animal from the length of four inches to that of three feet and a half; he had satisfied himself that in the whole province there was not, with the exception of the alligator, any Saurian or Salamander which exceeded six or seven inches in length, and he had convinced himself that it was oviparous, and that it propagated without losing its branchiæ. In 1766 Hunter, as we shall presently see, declared the Siren to be a complete form, on the most satisfactory evidence: the specimens dissected by him were brought from South Carolina in 1758. That the Siren is a perfect animal belonging to the perennibranchiate batrachians is now admitted by all zoologists. Cuvier indeed remarks (Règne Animal), that the branchia of Siren intermedia and Siren striata have been regarded as not participating in their respiration, and that in consequence Mr. J. E. Gray has formed them into the genus Pseudobranchus. Cuvier however adds, that it is, nevertheless, not difficult to see on their lower surface folds and a vascular apparatus, the use of which does not appear doubtful to him; and that M. Leconte has satisfactorily demonstrated that both these species, as well as Siren lacertina, are perfect animals. Cuvier remarks that the Siren should be judged of not after Amphiuma, but from itself. He accordingly procured some sirens, and saw an osteology so finished and so firm, that it was impossible to believe that they were not adult. The branchia of these individuals were perfectly entire, and their lungs completely developed, and rich in wellfilled vessels. No doubt therefore existed in his mind that the animals used both. each a groove for the lodgment of the posterior point of two slender bones, which proceed beside each other to the end of the muzzle. At their sides are attached two other bones, which are slender and pointed backwards, and which descend and widen far in order to raise the anterior edge of the jaw. Cuvier takes the first for the nasal bones, and the others for intermaxillary bones. These last are toothless, but their edge is trenchant, and furnished, when the animal is alive or well preserved, as well as the edges of the lower jaw, with a sheath which is nearly horny, is easily detached from the gum, and has its analogue in the tadpoles of the frogs. [SALAMANDRIDE, vol. xx., p. 328.] Between them, at the end of the osseous muzzle, is an aperture, but not that of the nostrils. In the recent animal it is closed, and the nostril is pierced on each side on the outside of the intermaxillary bone. In the crocodile the intermaxillary adheres to the external side of the nasal bone, and all the reptiles, except the crocodile, have the nostril on the outside of the ascending apophysis of the intermaxillary bone; but the peculiarity in the Siren is, that the intermaxillary ascending to the frontal bone entirely separates the nasal bone from the frame of the external nostril. The maxillary bone excludes the nasal in the same way in the chameleon. A very small bone, suspended in the flesh below the external nostril, and without any tooth, is the sole perceptible vestige of the maxillary bone. The cavity of the nostril is covered below with a simple ligamentous membrane. The internal nostril is situated on each side, near the commissure of the lips, between the lip and the palatine teeth. All the lower part of the cranium and the face is composed of a large and wide sphenoïd, which extends from the occipital hole to the intermaxillaries. The sides of the cranium, in the orbital region and the front of the temporal bone, are closed by a single bone, in which are pierced, forward, the olfactory aperture; farther back, the optic hole, and another for the first branch of the fifth pair, and probably for the small nerves of the eye. The inferior surface of this lateral bone forms part of the palate at the sides of the sphenoïd bone. It is plain that it performs the functions of He observes, that it had been objected that it would be the orbital part of the sphenoid bone, or what has been impossible for these animals to respire air without ribs or called the anterior sphenoïd, and that it fulfils in part those diaphragm; and without the power possessed by the tor- of the ethmoïd. Between it and the petrous bone is a great toises and frogs to cause it to enter by the nostrils, in order membranous space, in which is pierced the hole for the rest that, so to speak, it might be swallowed, because the nostrils of the fifth pair of nerves. The petrous bone and the lateral of the Sirens do not lead into the mouth, and the branchial occipital bone are perfectly distinct. It is in the petrous apertures must let it escape. But his own observations made bone only that the fenestra ovalis is pierced, or rather cut upon well-preserved individuals showed Cuvier that the nos-out, but the lower part of its frame is, nevertheless, comtrils in the siren do communicate with the mouth by a hole pleted by the lateral occipital and the sphenoïd. Its aperpierced, as in the Proteus, between the lip and the palatal ture, which is large, is directed a little downwards. In bone which carries the teeth. The membranous opercula the fresh state it is closed by a cartilaginous plate siof their branchiæ are muscular internally, and capable of milar to that in the Salamander. There is only a single hermetically sealing the apertures; then it is very easy for tympanic bone fitted obliquely by its posterior stem on the siren, by dilating its throat, to introduce the air into the superior surface of the petrous bone, and enlarging bethe mouth, and to force it afterwards, by contracting the low nearly like a trumpet, in order to furnish a large facet throat, into its larynx. Even without this structure of the to the lower jaw. Cuvier found neither mastoïdian, pterynostrils, the animal could produce the same effect by open- goïdian, jugal, superior occipital, nor basilary bone, and he ing its lips a little : a theory which Cuvier applies to the Pro- remarks that the occurrence of the two last is impossible, teus as well as the Siren. when the position of the suture, which separates the lateral occipital bones, is considered. To the palate, under the anterior and lateral part of the sphenoïd and orbital bones, are fitted two delicate plates beset with hooked teeth. They may be taken for the vestiges of vomers and of palatines, or, if it be preferred, of palatines and pterygoïdians; but Cuvier did not find sufficiently marked characters to warrant giving them those names. The first, which is the largest, has six or seven oblique rows of pointed teeth, making a kind of wool-card. Those of the middle have each twelve teeth; the anterior and posterior ones have less. The second plate has four rows of similar teeth, each row consisting of from five to six. The simultaneous existence, observes the same author, of a larynx and a trachea with a branchial apparatus not only permanent, but perfectly ossified in many of its parts, is also worthy of especial attention, and proves, as is evident in the frogs and salamanders, that the branchial apparatus is no other than a more complicated os hyoides, and not a combination of pieces proceeding from the sternum and larynx. He adds, that it is to the salamanders that the sirens approach most nearly by the structure of the head, although neither the general form nor the proportions of the parts have so near similarity. Having thus given a general view of the conformation of this extraordinary animal, we proceed to a sketch of the details of its ORGANIZATION. Skeleton. The skull of the siren is narrowed in front by reason of the excessive reduction of the maxillary bones, which consist only of a very small osseous point. Behind there is a strong occipital crest on the parietal and petrous bones. The pieces which form the lower jaw, instead of being transverse like the branches of a cross, are directed obliquely forwards. The parietal bones occupy the greatest portion of the upper part of the cranium. They have each in front a point, expanding so as to lodge between them the posterior part of the principal frontal bones, which have P. C., No. 1366. The lower jaw of the Siren is composed of four bones on each side; one of which forms the symphysis and the trenchant border of the jaw, which it invests externally up to near its posterior extremity. One cannot, Cuvier observes, avoid taking it for the analogue of the dental portion, but it is not the portion which carries the teeth, and it has only its trenchant edge invested in the fresh animal with a horny covering, analogous to that which forms the edge opposed to the upper jaw. The posterior extremity of this trenchant edge, more elevated than the rest of the border of the bone, serves for the coronoïd apophysis. The second bone forms the greatest portion of the internal surface and the posterior angle, and carries, above, the third, which is the VOL. XXII.-I articular tubercle. The fourth is a delicate and narrow The shoulder-blade of the Siren is slender, nearly cylin drical, narrowed in its middle, and augmented, on the spinal side, by a cartilaginous lamina. The clavicle and the coracoid are represented by two cartilaginous lobes, one directed forwards, the other much wider, proceeding upon the breast and crossing upon that of the opposite side. In the external border of this coracoïd cartilage, near and a little behind the articular fossa, is a bony semilunar lamina which is the sole representative of the bony coracoïd: but there is nothing similar for the clavicle. The humerus compressed laterally above, from before backwards below, and narrowed in its middle, has its extremities cartilaginous. It is the same with the two bones of the fore arm, both rather slender, and the internal bone or radius widened below. The bones of the carpus remain cartilaginous. Each of the four fingers has a metacarpian and two phalanges only. bifurcated, and ne oranches go to terminate on the articular posterior apophysis. Their very wide transverse apophyses are composed of two lamina united at their posterior border up to their common point; the upper, which is oblique, coming from below the anterior articular apophysis and from below the neighbouring part of the lateral crest, the lower coming from the sides of the body, to which it adheres by a horizontal line. The body below is also compressed into a sharp ridge (arête). In the vertebrae which carry the ribs, the upper lamina of the transverse apophysis is but little marked, and the point is stout and divided into two lobes for the two tubercles of the rib, as in the salamanders. Cuvier only found eight of these vestiges of ribs on each side, commencing from the second vertebra. The two last have the head simple. At the tail, the transverse apophyses, which have already become rather small, promptly disappear: the articular apophyses diminish also by degrees. The body of the vertebra takes a very compressed form, and gives below two small laminæ, which intercept a canal for the vessels, like the chevron bones in the lizards. eman sendt med got Anterior portion of the skeleton of Siren lacertina. a, dorsal vertebra seeu behind; b, the same seen before. There is no vestige of a pelvis, nor of any posterior extremity, either osseous or cartilaginous. Entire skeleton of Siren lacertina. Respiratory Organs.-John Hunter in 1766 gave the following accurate and interesting description of the two-fold respiratory apparatus of the Siren :-" On the posterior and lateral parts of the mouth are three openings on each side; these are similar to the slits of the gills in fish, but the partitions do not resemble gills on their outer edges, for they have not the comb-like structure. Above and close to the extremity of each of these openings, externally, so many processes arise, the anterior the smallest, the posterior the longest; their interior and inferior edges and extremity are Cuvier did not find in a large individual more than forty-serrated, or formed into fimbria: these processes fold down three vertebrae in the trunk and forty-four in the tail: but the individual which he described in 1807 had three more. These vertebræ, all perfectly ossified and complete, do not resemble in his opinion those of any of the reptiles of which he had previously treated, nor indeed of any other animal. Their bodies have their two articular faces hollow and united by a cartilage in the form of a double cone, as in the fishes. Their articular apophyses are horizontal, and the posterior apophyses of one vertebra lie on the anterior apophyses of the other. A horizontal crest on each side goes from the anterior to the posterior. In lieu of a spinous apophysis, they have a vertical crest, which at half its length becomes and cover the slits externally, and would seem to answer the purposes of the comb-like part of the gill in fish. At the root of the tongue, nearly as far back as these openings reach, the trachea begins, much in the same manner as in birds. It passes backwards above the heart, and there divides into two branches, one going to each lobe of the lungs. The lungs are two long bags, one on each side; which begin just behind the heart, and pass back through the whole length of the abdomen, nearly as far as the anus. They are largest in the middle, and honeycombed on their internal surface through their whole length.' (Phil. Trans lvi., 1766.) In the Museum of the Royal College of Surgeons in Lon- | vular protuberance which projects into it from the dorsa. don this part of the organization is well illustrated. No. aspect. On the opposite side of the preparation the cra1062 presents a Siren lacertina, with the ventral parietes of nium and upper jaw are removed to show the apertures the abdomen removed, together with all the viscera, except leading from the mouth to the lungs and gills, the simulthe lungs, which have been distended with spirit. These taneous existence of which through life forms the chief cha. commence immediately below the pericardium, and extend racteristic of this tribe of truly amphibious reptiles. No. 913 almost to the anus. A bristle is passed through the trachea, is the heart of a Siren. The auricle, consisting of two and the laryngeal orifice is exposed by the removal of the chambers, appears as one cavity externally. It is remarkcranium. The branchiæ are external, three on each side, able for its large size, its weak parietes, and the number of and suspended to four cartilaginous arches of the hyoid bone. fimbriated follicular processes which it sends off, and The three internal branchial apertures of the left side may which gives it an appearance similar to the branchial be seen. No. 1063 exhibits the right side of the head of a divisions of the vena cava in the cephalopods. The larger specimen of Siren lacertina, showing the branchial ventricle is here seen to be slightly bind at the apex. arches and gills of that side. The first and fourth branchial The artery is membranous at its commencement. The bulb arches are fixed, the intermediate ones only being free. is here laid open to show the internal valvular projection. Their concave margins are provided, as in many fishes, with No. 913 A presents the heart and pericardium of a Siren small pointed processes, which lock into one another and lacertina, prepared to show the internal structure of the defend the branchial passages. The gills increase in size auricles and ventricle. White bristles pass from the veins of from the first to the third, which is suspended to both the the body into the right auricle, and black ones through the third and fourth arches. They are subdivided and fim- pulmonary veins into the left auricle. This is much smaller briated inferiorly, where the surface is most vascular: the than the right auricle, corresponding to the quantity of branchial arteries may be seen injected on the convex side blood which it receives. The pulmonary veins unite into a of the cartilaginous arches. The origin and subsequent common trunk, which seems to pass through the great sinus reunion of the branchial vessels to form the aorta are shown of the veins of the body, but it adheres to the parietes of in the preparation No. 914 (from which the present was that sinus by its posterior surface. Here Professor Owen taken), noticed below. No. 1064 is a portion of the lungs of remarks that it is probably this remarkable structure which led the same Siren, laid open to show the ramifications of the Hunter to suppose that the sinus was part of the pericardium, pulmonary artery, which form a vascular network upon the and that the vena cava opened into it. The Professor then internal surface of this simple respiratory bag. (Catalogue, quotes Hunter's description, above given, and adds, with vol. ii.) truth, that all anatomists since Hunter's time have concurred in ascribing but one auricle to the heart of the Siren, and that Cuvier regards this simple structure of the central organ of the circulation as common to the Batrachian order of reptiles. The outward form of the auricle, observes Mr. Owen, naturally suggests such an idea, and it is only in favourable specimens that the true structure, as it is shown in this preparation (made by him), can be made out. The ventricle is connected to the pericardium, not only by the reflection of the serous layer from the bulbus arteriosus, but by a duplicature of the same membrane, which passes from the lower third of the posterior edge of the ventricle, and incloses the coronary vein: this vein is continued from the apex of the ventricle to the sinus. The muscular parietes of the ventricle are about a line in thickness, and of a loose fascicular structure. The cavity is partially divided by a rudimentary septum, which extends from the apex half way towards the base of the ventricle, and there terminates in a concave edge directed towards the orifice of the artery, The whole inner surface is reticulated by decussating carnea columnæ, one of which has been detached from its connection to the septum, which intervenes to the two auri. cular apertures, and which supports the valvular structure that closes them from within. The artery and bulbus arteriosus are laid open, showing in the latter the remarkable valvular projection described by Hunter. In conclusion, Professor Owen remarks that the vessels on the back part of the talc, which supports the preparation, are, the inner ones, the pulmonary arteries, the outer ones, the jugular veins or anterior cava. No. 914 is the anterior part of the body of a large Siren lacertina, prepared to show the heart and principal vessels injected. The fimbriated structure and magnitude of the auricles are well seen when thus distended, and they then advance forwards on both sides of the ventricle and bulb, so as almost to encompass those parts. The two divisions of the venous sinus may be observed below the ventricle, with the termination of the coronary vein and the attachment of the ventricle to the sinus. Behind the ventricle appear two superior cave which terminate at the sides of the sinus. The portions of the lungs which remain are laid open to show their reticulate structure, and the relative positions of the pulmonary arteries and veins: white bristles are placed in the former, and black ones in the lateral vessels. On the left side of the preparation, the origin of the pulmonary artery, from the posterior branchial arch, is shown. The remainder of the branchial vessels, with the exception of small branches to the head, are collected into one trunk, which unites with the corresponding vessels of the opposite side to form the aorta or systemic artery. The tongue, the interior of the air tube, the internal branchial aperture, and the branchia of the left side, the eye and nostril, and structure of the integument are also favourably displayed in this preparation. [PROTEUS and PROTOPTERUS.] Circulating System.-John Hunter describes (1766) the heart of the Siren as consisting of one auricle and ventricle. 'What answers,' says Hunter, to the inferior vena cava, passes forwards above, but in a sulcus of the liver, and opens into a bag similar to the pericardium: this bag surrounds the heart and aorta as the pericardium does in other animals; from this there is an opening into a vein which lies above, and upon the left of the auricle, which vein seems to receive the blood from the lungs, gills, and head, is analogous to the superior vena cava, and opens into the auricle which is upon the left ventricle. The aorta goes out, passing for a little way in a loose spiral turn, then becomes straight, where it seems to be muscular: at this part the branches go off, between which there is a rising within the area of the aorta like a bird's tongue, with its tip turned towards the heart. This account of the vena cava opening into the cavity of the pericardium may appear incredible; and it might be supposed that, in the natural state of the parts, there is a canal of communication going from one cava to the other, which being broken or nipt through in the act of catching or killing the animal, would give the appearance above described. I can only say that the appearances were what have been described in three different subjects which I have dissected, and in all of them the pericardium was full of coagulated blood. But besides the smallness of the subjects, it may be observed that they had been long preserved in spirits, which made them more unfit for anatomical inquiries. They had been in my possession above seven years.' (Phil. Trans., lvi.) In the Museum of the College of Surgeons the preparation No. 912 shows the anterior part of the body of a Siren lacertina. The ventral parietes have been removed, together with the pericardium, to show the heart in situ. It is of an elongated form, and consists of a large fimbriated auricle, divided internally into two chambers, and of a flattened oblong ventricle, giving off a single artery, which, after a half-spiral twist, dilates into an elongated fleshy bulbus arteriosus. The blood from the body passes into a large membranous sinus formed by the union of the two anterior vena cava with the large posterior cava. The latter vessel pours its blood into the sinus by two orifices on either side a septum, which extends forwards as far as the openings of the anterior cava, where it terminates in a free semilunar margin; the sinus is then continued forwards, and terminates in the chamber analogous to the right auricle. White bristles pass from the posterior cava through the sinus on either side the septum into the anterior cava. A black bristle is passed through the right pulmonary vein into the trunk common to the two, which traverses but does not communicate with the sinus proper to the veins of the body, and terminates in the chaniber analogous to the left auricle. The bulbus arteriosus is laid open, to show the val We now proceed to lay before our readers such other pre- | sides the parts concerned in the circulatory and respiratory parations in this noble collection as illustrate the circulating functions, the stomach, duodenum, liver, pancreas, and system in animals approximating to the perennibranchiate spleen are well shown in this preparation. No. 917 exhibits batrachians, so that the student may compare this part of the heart, pericardium, and trachea of the last-noticed their organization with that of the Siren. species. Here the ventricle is laid open to show the loose, fasciculate, muscular structure, which, as in the Testudo Indica, occupies the whole of its cavity. The bulb of the aorta is laid open to show the two rows of semilunar valves, three in each row, and the origins of the branchial arteries. The preparation is suspended by the pericardium, behind which is the flattened air-tube, in which distinct cartilaginous rings may be seen. (Catalogue, vol. ii.) No. 915 shows the anterior part of the body of an AMPHIUMA (Amph. means, Garden), prepared to show the heart and great vessels in situ. Professor Owen states that the blood is returned from the body, as in the preceding species, by two anterior vena cava, and one large posterior cava, which form by their union a membranous sinus. The auricles or venous chambers of the heart are proportionately smaller and less fimbriated, and are situated more to the left and superior part of the ventricle. The ventricle is connected to the pericardium at its apex, and gives off from its opposite extremity a single artery, which, after a half-ration. spiral turn, dilates into a large bulb, which is broader and shorter than in Siren lacertina, and is grooved externally. The two pulmonary arteries are given off from the posterior part of the extremity of the bulb, which then divides into two branches, each of which again subdivides on the side of the œsophagus. As there are no external gills, so there are no lateral branches sent off from the branchial arteries; but these, after winding round the arches of the hyoïd bone, terminate in a single trunk on either side, and form by their union the aorta, which is seen, injected, behind the pharynx. On the left side of this preparation the internal branchial aperture is preserved, and on the right side the branchial arches of the hyoïd bone are shown. The lungs are laid open so as to display their reticulate and longitudinally plicate structure, and the relative positions of the pulmonary arteries and veins. Professor Owen further observes that this preparation is figured by Rusconi (Amours des Salamandres Aquatiques, pl. v., fig. 8) as a portion of the adult Siren lacertina, which he supposes to have lost the external branchiæ, and to have acquired the posterior extremities in a manner analogous to the salamanders; and that Rusconi endeavours to invalidate the opinion which Hunter, after an extensive and minute comparison of their entire structure, had formed of the specific difference of the Amphiuma and Siren, as well from each other as from the Kattewague or Menopoma of Harlan. The manuscript alluded to by Rusconi, and which contains detailed accounts of the anatomy of Amphiuma and Menopoma, as well as of the Siren, is given entire in the description of the plates illustrative of the 2nd vol. of the Museum Catalogue, where (plates xxiii. and xxiv.) the circulating and respiratory organs of the 'Chuah Chisstannah, or Crawfish-eater, or Kattewagoe' (Menopoma Alleghaniensis, Harlan [SALAMANDRIDE, vol. x.x., p. 332], are beautifully displayed; and Professor Owen remarks that the conclusions as to the distinctions of these amphibia to which Hunter arrived, have been subsequently confirmed by a similar series of investigations instituted by Cuvier, and above noticed. Generative System.-No. 2695 exhibits the posterior part of a Siren lacertina, with the ventral parietes of the abdominal cavity removed to display the female organs of geneThe ovaria are seen as two irregular elongated bodies, situated on each side of the root of the mesentery, and bearing impressions of the convolutions of the intestines. They contain innumerable minute ovisacs of a greyish colour, with a few others of a larger size, and of a very dark colour. The oviducts are external to the ovaria, and are attached to the sides of the spine, each by a broad duplicature of peritoneum: they commence anteriorly by a simple, elongated, slit-like aperture, without fimbriated margins, and are immediately disposed in about twenty parallel transverse folds, which gradually diminish, and finally cease about three inches from the cloaca, where the oviducts open behind the rectum upon small prominences: bristles are placed in these outlets. The contracted allantoïd bladder is seen anterior to the rectum: the posterior extremity of the kidney extends behind the oviducts, a short way beyond the cloaca. No. 2696 shows the anterior extremity of the oviducts and liver of a Siren. The oviducts are much attenuated at their commencement, but soon increase in size, and become thicker in their parietes. (Catalogue, vol. ii.) No preparation of the male organs of the Siren appears to exist in the College Museum; but there are two illustrative of those of Amphiuma and Menopoma, which we proceed to lay before our readers. No. 2397 is the posterior moiety of an Amphiuma (Amphiuma didactylum), with the abdominal cavity laid open, and exposing to view the termination of the intestinal canal, supported by its broad and simple mesentery, the termination of the right lung, the long allantoïd bladder attached by a duplicature of the peritoneum to the mesial line of the abdomen, and the testes with their adipose appendages: the latter may be observed projecting on each side of the root of the mesentery; and behind them are the testes, elongated, subcylindrical, ash-coloured bodies, tapering at both extremities: the vasa deferentia descend in the form of white ligamentous tubes, and finally open into the posterior part of the termination of the rectum, which is laid open. The renal organs are almost concealed by the parts above described: they have been injected. No. 2938 exhibits the male organs, kidneys, allantoïd bladder, and large intestine of the Menopome (Menopoma Alleghaniensis). The testes in this subject are less elongated, and of a more compact oval, thus indicating a further stage of advancement above the class of fishes. The efferent vessels leave the testis at a longitudinal groove at their posterior and internal surfaces, at the line of reflection of the supporting processes of peritoneum, and on each side unite to form a vas deferens, which descends along the edge of a process of peritoneum external to the kidneys, and finally opens into the termination of the rectum, as in the Amphiume. The kidneys are opake white bodies, which, beginning by small extremities near the lower end of the testes, slightly enlarge as they descend to the cloaca. The injected aorta occupies their posterior interspace, and there sends off the arteries for the hinder extremities. (Catalogue, vol. ii.) No. 916 of the same museum exhibits the lower jaw, tongue, fauces, with part of the abdominal viscera, and the heart in situ of Menopoma Alleghaniensis. The greater part of the pericardium has been removed. The ventricle is of a flattened triangular form, resembling that of osseous fishes: the auricles are smaller in proportion than in the Siren, and are situated wholly to the left of the ventricle. The veins of the body terminate in a membranous sinus situated below the auricles. The aorta, after making a spiral turn to the left side, dilates into a large bulb which gives off four vessels on each side. The first or posterior pair are the smallest, and ramify on the oesophagus and lungs; but they are not distinctly shown in this preparation. The second and third pairs are the largest they are seen passing outwards, and winding round the arches of the hyoid bone. The two branches unite on each side, and, after sending off small arteries to the head, converge on the posterior part of the oesophagus, and unite to form the descending aorta. The fourth small pair of arteries pass outwards, and wind over the anterior part of the first hyoïdian arch: they send off in this course some small arteries to the head, and ultimately unite with a cephalic branch given off from the united trunk of the third and second branchial arteries. The right lung is here preserved, and a black bristle is inserted into it from the trachea. White bristles are placed in the right branchial the Mud Iguana. Garden was of opinion that it feeds aperture, which is left entire, showing the absence in this on serpents, and that it uttered a cry similar to that of a form, as in Amphiuma, of external gills. On the left side young duck; but Barton contests these statements. Its the branchial arches of the hyoïd bone are preserved. Be-food is generally believed to consist of earth-worms, insects, Siren lacertina grows to the length of three feet: its colour is blackish. The feet have four toes, and the tail is compressed into an obtuse fin. This Siren inhabits the marshy grounds of Carolina, especially those where rice is cultivated. It lives in the mud, from whence it makes excursions, sometimes on land and sometimes in the water. From the swampy places by the sides of pools and under the overhanging trunks of old trees where it is found, it was called by the inhabitants SIR &c. There is now (Sept., 1841) a fine lively specimen in the parrot-house in the garden of the Zoological Society in the Regent's Park. It is kept in a vessel of pond-water with a deep bottom of mud, in which it bides itself, and is twenty inches long, as large as the wrist of a stout child of six months old, and very eel-like in its movements and appearance. About a dozen and a half of earth-worms are supplied to it as food every other day. Siren striata is blackish, with two longitudinal yellow stripes on each side; has only three toes on each foot, and is about nine inches in length. Siren striata. a 61 'The nucleus did not partake in the same degree with these varieties of form, but maintained a more regular elliptical form; the varieties in question appearing to depend on pressure acting upon the capsule and the coloured fluid surrounding the nucleus. Yet when the ellipse of the blood-disc was, as it happened in a few cases to be, longer and narrower than the average, the form of the nucleus presented a similar modification of size. 'The following is a table of the averages of many admeasurements of these blood-discs, made with the screw micrometer*: 'Long diameter Short diameter Long diameter of nucleus English inch. 1-850th to 1-870th 1-1000th 1-3800th (as viewed edgeways covered by the capsule). 'The nucleus was circumscribed by a double line, the outer one more regular than the inner one, which appeared crenated. This appearance was due to the structure of the nucleus, or the contents of the nucleolar capsule, which was indicated by the outer line. These contents consisted, in every blood-disc examined, of a number of moderately bright spherical nucleoli, sufficiently distinct to be counted, when viewed by a Powell's 1-10th inch objective, with the eye-piece, magnifying 700 linear diameters: the ordinary number of nucleoli seen in one plane or focus being from twenty to thirty, the total The facility as number was of course much greater. well as certainty of the demonstration of such a structure in a, head and anterior part seen in profile, showing the branchin and foot. Whilst the article was passing through the press, Professor Owen was so good as to send the following highly in-rately resisting, elastic, as was easily seen by the flattening teresting observations on the blood-globules of the Siren for insertion in this work: Among the important generalizations which the numerous observations of recent microscopical anatomists have enabled the physiologist to establish respecting the form and size of the blood-discs in different classes of animals, the most interesting seems to be that which Professor Wagner has enunciated respecting the relation of the magnitude of the blood-disc to the persistence of the branchial apparatus in the Batrachian order of reptiles on the occasion of his description of the blood-discs of the Proteus anguinus. The absolute size of these particles in that perennibranchiate reptile, in which they may be distinguished by the naked eye, renders them peculiarly adapted for minute investigations into the structure of the nucleus and capsule of the blood-disc: but the value of the relation between their size and the persistency of the external gills must depend upon the correspondence of other perennibranchiate reptiles with the Proteus in this respect. The superior size of the blood-discs of the newts to those of the land-salamanders and tailless Batrachians has been confirmed by Professor van der Hoeven's observations on the blood-discs of the gigantic newt of Japan (Sieboldtia, SALAMANDRIDE, vol. xx.. pp. 331, 332), of which a fine specimen has been for several years kept alive at Leyden; and I have been able to add another instance of the still greater relative size of the blood-discs in the perennibranchiate reptiles by the examination of those of the largest existing species of that family, the Siren acertina, of which a specimen twenty inches in length is now (October 15th) living at the Zoological Gardens. The blood was obtained from one of the external gills, and immediately subjected to examination. The blood-discs presented the elliptical form which hitherto without exception has been found to prevail among the airbreathing oviparous vertebrated animals: the ellipse was not quite regular in all the blood-discs; several were sub-ovate, a few slightly reniform and thicker at the more convex side: all were as compressed, or disc-shaped, as in other Batrachians, with the nucleus slightly projecting from each of the flattened surfaces. of the parts of two blood-discs that might come in contact, and the recovery of form when they were floated apart. 'As the fluid contents of the blood-disc in part evaporated during the process of desiccation, the capsule fell into folds in the interspace between the nucleus and the outer contour, these folds generally taking the direction of straight lines, three to seven in number, radiating from the nucleus.' (R. Owen, Sept. 25, 1841.) Blood-discs of Man aud Siren, drawn by the camera lucida under a magni fying power of 700 linear dimeusious. a, Human blood-discs; a', ditto viewed edgewise; b, Siren's blood-disc; b, ditto viewed edgewise; c, folds of external capsule, produced by desiccation; d, capsule of nucleus; e, nucleoli. SIRENS (Epйves) are described in the 'Odyssey' as two maidens who sat by the sea and so charmed with their music all who sailed by, that they remained on the spot till they died. Ulysses, by the direction of Circe, had himself tied to the mast, and stopped the ears of his companions with wax, by which means he was able to hear their music, and escape from its influence. (Od., xii. 39, &c., 169.) The 1 was in.debted to Mr. Stokes for the use of the one attached to his ad mirable microscope by Powell. |