« AnteriorContinuar »
would be liable to be torn and bruised. Add to these incon- | into the gasteropod by placing, side by side, some intermediate veniences the fact that it would be without eyes or feelers in the forms between the more typical turbo and the river-mussel fore-part of the body to direct its course, or to take observations (Unio). In patella (the limpet) it will be seen that the gills are of what occurred, and we may judge that the benefits of travel still on both sides of the animal, as are also the muscles, though would be quite outweighed by its dangers and troubles. In the these have no longer the office of closing the shell, which, in this gasteropods, therefore, both shells are consolidated into one, and case, is consolidated into an equilateral cone. In the bonnet drawn out in an upward direction, so that, while the more deli-limpet one side of the breathing organs has been aborted, while cate organs are securely lodged, the edges of the shell's mouth in turbo both the breathing apparatus and muscles of one side are withdrawn from the ground.
are gone, and the whole animal is twisted, in its upper part, The gills are removed out of harm's way in a singular manner. into a one-sided spire. In this case a rounded horny plate is
I., II., III., IV. DIAGRAMS OF UNIO, PATELLA, CALYPTREA, AND TURBO, TO SHOW THE STAGES OF TRANSITION FROM THE CONCHIFER TO THE TYPICAL
GASTEROPOD. V. A SINGLE SET OF TRANSVERSE TEETH FROM (1) A SEPHORATED GASTEROPOD AND (2 AND 3) UNSEPHORATED GASTEROPODS. VI.
SHELL OF Cassis. VII. PALUDINA. VIII. SECTION OF CERITHIUM, Ref. to Nos, in Figs.-I., II., III., IV. 1. l', lips or tentacles ; 2, mantle ; 3, shell muscles ; 4, sills; 5, foot; 6, position of the liver ; 7,
byssus ; 8, operculum. VI. 1, spire ; 2, suture ; 3, aperture ; 4, outer lip; 5, inner lip; 6, anterior canal for passage of the siphon ; 7, posterior canal; 8, varices. VII. 1, umbilicus. VIII. 2, columella.
Those on one side (usually the right) are brought right up and developed on the upper part of the foot, or rather tail of the placed on the animal's back, and there enclosed by a fold of the creature, and this, when the animal pulls back its head and leathery skin, and placed partially in the last or largest part of thin foot into the shell, closely closes the aperture. This the shell cavity, while those of the other side are entirely operculum, as it is called, is supposed to be the representative aborted or dispensed with. This arrangement gives a one of the horny byssus of the bivalve, being, as will be seen, sidedness to the animal, and, perhaps, is the determining canse similarly situated. of the shell being made more compact in the method peculiar to The alimentary canal commences with a mouth armed with gasteropods, namely, by being twisted into a one-sided spiral or hard parts. These are different in different creatures; but in helix, as it is technically called. The head, with its feelers, all there is a fibrous plate, bearing teeth, placed on a cushion on eyes, and ears, can be thrust out from the shell and stretched the floor of the mouth. These teeth are usually directed backwell forward, so as to gain some acquaintance with those external wards ; sometimes the plate in which they are set is very long objects which come within the line of march. In the illustration from point to back, the teeth being disposed in small cross it is shown how the conchifer may possibly have been modified rows set in parallel lines from one end of the plate to the other. This is more especially the case in the carnivorous sea-snails, in All the land, and most of the fresh-water enails have lungs, which it is associated with a long extensible proboscis. In the and belong to the sub-class Pulmonifera, while the sea-souls land and fresh-water gasteropods belonging to the order have gills, and belong to the other sub-classes. Thus we see Pulmonifera, the number in a cross direction is very great, but repeated in the Mollusca the two different kinds of breathing the lingual ribbon is much shorter. This tooth-bearing ribbon organs which are suited to aquatic and aërial life, which, in the is set on a muscular pad, which can move it backward and vertebrates, are represented by the gills of fish and the lungs of forward, so that the little flinty teeth act as a fine file. It is the higher orders. From this we may infer that a gill is the curious that these teeth are composed neither of horn nor shell necessary form of a water-breathing apparatus. (CaCO3), but of silica (SiO,) or flint. They are, of course, liable There is yet another sub-class of gasteropods called to be worn away; but the ribbon is formed from behind as fast Nucleobranchiata, or Heteropoda, which have various forms of as it wears away in front; and in some species, a considerable breathing organs; but these are so different in the whole of length of it lies coiled up in a sac or pouch, which stretches their structure from the rest that it becomes a question whether away from the mouth, ready to supply the place of the continual they should be classed with the gasteropods at all. wear and tear. A few examples of the pattern of the teeth are The central organ, which aids the circulation of the blood, is given in the engraving, in which only one transverse row of situated in the typical gasteropods in the partition or diaphram, three different species is given. The mouth is very muscular, as it is called, which lies between the breathing chamber and and has on its front and upper wall a broad horny jaw, which the chamber containing the viscera. It is always at the hind is flat, with a cutting edge directed downward. It is of various part of this, and receives the blood from the gills, or central shapes, and is often toothed on its lower edge. In some sea- vessel of the lungs, into a chamber or auricle. From this it snails the mouth-cavity is furnished with a long trunk, which passes through a valve to the more muscular ventricle, and is can be unfolded from within, and used to grasp objects while driven by this into a vessel which almost immediately divides they are played upon by the file-like tongue. Inside these into two, one of which goes forward to the mouth and foot, and trunks there is sometimes a toothed circle or collar of pointed the other backward to the liver and all thoso organs which are fangs, which very much strengthen the hold that the creature situated in the recesses of the shell or hind cavity of the abdohas on its prey. It is singular that this tooth-bearing tongue men. The blood, thus distributed by vessels, is said to escape is found universally, not only among the gasteropods, but also from them into the general cavity of the body, and from thence among all the higher orders of the Mollusca, so that some enters by wide openings to the veins which convey it to the gills classifiers have associated these together as the Odontophora, or or lungs. In the case of the lung-breathers it enters the tooth-bearers.
diaphragm from behind, and runs in two main vessels along the We proceed to describe the alimentary canal as it occurs margins of this organ, and then sends off smaller • vessels or in the arion, or common black slug, noticing such marked dif- sinuses towards the central vessel. In the Prosobranchiata the ferences as occur in some other orders. A very small throat sexes are distinct; but in the Pulmonifera and Opisthobranleads from the roundish buccal cavity, and this gradually dilates chiata the sexes are united in one individual, and the organs in until it ends in a wider stomach. On the sides of the throat the former are of very complicated and peculiar structure. In are situated two large glands for secreting saliva ; but, though the neighbourhood of the heart there is an organ which is conbonnd to the exterior of the throat by vessels, they discharge sidered to be a kidney, which eliminates the azotised products their secretion into the back part of the mouth by two ducts, caused by the wear and tear of the vital action. This organ which pass between the nervous collar and the attenuated seems also, in some species, to have the office of introducing portion of the throat. The stomach is of various shapes in the water into the blood-system from without, as it has an opening slugs; but in the example before us the hind part forms a kind on the one side into the breathing-chamber, and on the other of globular bag, and the two ducts from the liver enter just into the pericardium or external heart-chamber. before this rounded portion. The intestine leads from the globe The front part of the mantle-fold, which covers in the directly forward, so that this globular part occupies an acute breathing-chamber, is thickened into a collar, and this is the angle in the course of the alimentary canal, and then, after being instrument for secreting the shell. The shape and foldings of bent backwards and forwards two or three times, runs to a small this edge of the mantle give rise, in the process of growth, to all orifice situated at the neck of the animal on the right side, close those beautiful shells whose variety of colours and shape must to the aperture of the breathing chamber. The stomach and be known to the reader. intestine are closely embraced by lobes of the very large liver, One of the characteristics of the gasteropods is the immense which is so bound to them as to be with difficulty unravelled amount of sticky mucus they are constantly exuding, and which In the case of the spirally-coiled and shell-bearing gasteropods, makes, in the land-slugs, a serious draught on their nutritive the largest masses of the liver are situated in the small end of system. This is secreted by glands all over the skin, but also, the spiral shell. In the aplysia (the sea-hare), and some other in some species, by special larger glands on the back of the of the gasteropods allied to it, the interior of the stomach is neck. studded with shelly plates and spines, thus converting it into a The nervous ganglia, though they probably consist of the gizzard.
same elements as in the Conchifera, are gathered together so The breathing organs of the Gasteropoda are very various, as to form a ring round the throat, situated at the Carrow part and they have been made use of to divide the class into sub- just behind the buccal mass. The muscular system is almost classes and orders, Thus there are four main sub-classes wholly confined to the skin, except that a broad muscle arising founded mainly on these organs. In the Opisthobranchiata the from the lower part of the body runs to the head, and slips of gills are branched like a tree, or gathered together in bundles this muscular sheet also go up the tentacles, so that, when in and placed on the hind parts of the body behind the heart, and contraction, the tubular tentacle and eye-stalks are pulled into are either naked or only partially protected by a fold of the the body at the same time as the head is withdrawn. In the mantle or shell. In the Pulmonifera there is a chamber common snail the eye-tentacles are the longest, and are set situated over the neck, and covered completely in by a thick highest on the head, while the lower pair is simply tactile. In fold of the mantle. It only receives air through an aperture, many sea-snails there is only one pair of tentacles, the ends of which can be closed by a muscle running round it. The walls, which are feelers, while the eyes are set on the sides or bases of and especially the floor, of this chamber have large blood-vessels these. The eyes, themselves, are not highly organised, being in them, and so constitute a kind of lung in which the blood is little more than a nerve expanded in front of a dish of black aërated. In the Prosobranchiata the arrangement as to the pigment, and placed behind a transparent cornea.
Ear-s208, chamber is much the same, but in the chamber lie one or two with round ear-stones in them, are found in many Gasteropoda. gills, usually of a comb-like or feathery form, and in these, and The Gasteropoda are the most typical class of the Molluscanot in the walls of the cavity, the blood becomes oxygenated. that is, they are the central group, showing fewer points of In the carnivorous sea-snails the aperture is converted into a relation to the other sub-kingdoms than the other classes, and canal or siphon, which is often very long, and which has an possessing a very large number of species nearly allied to one anterior canal in the aperture of the shell for its accommodation, another, so that there are fewer gaps in the series. They, in thus constituting the difference between the round-mouthed fact, occupy a similar position with regard to the Mollusca as (Holostomata) and channelled (Siphonostomata) shells, as shown the insects do to the Articulata, or the osseous fishes do to the in the illustration.
LESSONS IN ARCHITECTURE-XVIII.
burning lava, and of course are found in an incomplete state ;
they turned on pivots, and were fastened by bolts which hung PRIVATE HOUSES.
upon chains. Bedsteads are found, made both of wood and HOXER, in his “Odyssey," informs us that the houses and even iron ; but their beds were made generally of carpets and vests, the palaces of ancient Greece were constructed of wood ; and spread upon the ground. The articles of household furniture among others he particularly describes that of Ulysses, at Ithaca. and convenience found in these remarkable ruins are utensils of It is stated that the private houses of the early Romans were every kind in silver, brass, stone, and earthenware, with vases small, and that the doors were left unclosed during the principal of every size and adapted to every use; trumpets, bells, gridmeal. As wealth and luxury increased, the size of their houses irons, colanders, saucepans (some lined with silver), kettlos, became so great as to accommodate, in no very extraordinary ladles, moulds for jelly or pastry, urns for keeping water hot on cases, no less than four hundred slaves under a single roof. The the principle of the modern tea-urn, horn-lanterns, spits, and, height of private houses at Rome was restricted by the Emperor in fact, every article of kitchen or other furniture used by us, Augustus to seventy feet; but the irregularity of the city be- except forks; chains, bolts, scourges, dice (some said to be came so great, that in one sense its conflagration by Nero turned loaded); a complete toilet, with combs, thimbles, rings, paint, out a public good. For, being passionately fond of building, pins, earrings, pearls, etc. But for more enlarged details, we this made way for his architectural plans, and rendered Rome must refer to the work of Sir William Gell and J. P. Gandy, afterwards a regular and splendid city. Notwithstanding these entitled “Pompeiana,” in which there is given a detailed account private architecture of the Romans. There was a general ab. Of The excavated towns above mentioned being small, furnished sence of chimneys and of windows ; and the only light received' specimens chiefly of houses inhabited by Romans of the middle in the rooms was through an aperture formed in or over the and lower classes. At Rome itself, the excavations of the villa door. In these respects, therefore, they were little removed Negroni have made us acquainted with the nature of purely from the rude cottages of the poor still to be seen in the remote Roman houses, and of the higher class. To this may be added parts of our own country. One reason for the neglect of com- the following description, by himself, of the winter residence of fort in their private dwellings was, that they were not a do- Pliny the Younger, at Laurentinum, situated at the distance of mesticated people; they lived in public and for the public, and seventeen miles from Rome, which gives us a more distinct contheir society was to be found in the Forum and public porticoes. ception of the villa of a wealthy nobleman of that city:A military people are sure to be thus circumstanced ; and France, “My villa is large enough to afford all desirable accommodaat least in Paris since the first revolution, has presented a simi. ; tion without being extensive. The porch before it is plain, but lar spectacle to the observer. Her inhabitants live in cafés, and not mean, through which you enter a portico in the form of the in clubs or societies, but not at home.
letter D, 'which includes a small but agreeable area. This The arrangement of ancient houses greatly differed from the affords a very commodious retreat in bad weather, not only as modern in the formation of their internal courts. These were it is enclosed with windows, but particularly as it is sheltered usually constructed so that each was surrounded by apartments by an extraordinary projection of roof. From the middle of which, when lighted from within, prevented the domestic con- this portico you pass into an inward court, extremely pleasant, cerns of the family from being overlooked by any one not and thence into a handsome hall, which runs out towards tho included within the walls. From a passage in Plautus, it does On every side of this hall there are either folding-doors not appear that this construction always answered the purpose ; or windows equally large, by which means you have a view and in Seneca mention is made of the annoyance to which the from the front and the two sides, as it were, of three different neighbours were subject from the disorderly conduct of those seas; from the back you see the middle of the court, the portico, persons who changed night into day by indulging in the false and area; and by another view you look through the portico refinement and late hours of the age in which he lived. In into the porch, whence the prospect is terminated by the woods the Roman houses, also, there appears to have been, after the and mountains which are seen at a distance. On the left-hand Eastern fashion, a remote or inner court for the apartments of side of this hall, somewhat farther from the sea, lies a large the females, accessible only by an outer court for those of the drawing-room, and beyond that a second of a smaller size, which males, and of the servants. The information conveyed to us in has one window to the rising and another to the setting sun. the works of Vitruvius has received singular illustration and The angle which the projection forms with this drawing-room confirmation within a period less than a century, from the exca- retains and increases the warmth of the sun; and hither my vations at Pompeii, Herculaneum, and Stabia, cities which were family retreat in winter to perform their exercises. Contiguous overwhelmed by a tremendous eruption of Vesuvius in A.D. 79, to this is a room forming the segment of a circle, the windows and which contained houses built and inhabited by Romans of which are so placed as to receive the sun the whole day; in belonging to the age of Vitruvius. These excavations exhibit the walls are contained a set of cases, which hold a collection of curiously paved streets, having the tracks of carriage-wheels such authors whose works can never be read too often. Thence marked on them, and houses built of brick and rubble-work pat you pass into a bed-chamber through a passage which, being together with mortar, all the materials being of very inferior boarded, and suspended over a stove which runs underneath, quality, except the interior coating of plaster, to which they tempers the heat, which it receives and conveys to all parts of appear to have been chiefly indebted for their durability. This this room. The remainder of this side of the house is approplaster was composed of lime and pounded marble, a substitute priated to the use of my slaves and freedmen; but most of the for stucco, and by its use a perfectly smooth and polished sur- apartments are neat enough to receive any of my friends. In face was obtained, nearly as hard as marble. With this kind of the opposite wing is a room ornamented in a very elegant taste; stucco the smallest apartments at Pompeii are found to be next to which lies another room, which, though large for a lined; and this lining is painted with various and brilliant parlour, makes but a moderate dining-room. Beyond is a bedcolours, and embellished with subjects either in the centre or at chamber, together with its ante-chamber, the height of which equal distances, like panels. Painted imitations of variegated renders it cool in summer, as its being sheltered on all sides marbles, forming, perhaps, a species of scagliola, also decorate from the winds makes it warm in winter. To this apartment the walls of their houses. Few blocks of real marble are found, another of the same sort is joined by a common wall. Froma except in monuments and public buildings; though, in imitation thence you enter into the grand and spacious cooling-room beof the wealthy Romans, the Pompeians inserted pieces or slabs longing to the bath, from the opposite walls of which two round of this material in their walls, and employed art to give them basins project, sufficiently large to swim in. Contiguous to this higher tints than those they possessed by nature. They also is the perfuming-room, then the sweating-room, and next to that discovered a method of veining slabs with gold; and leaves of the furnace which conveys the heat to the baths. Adjoining this metal covering the beams, walls, and even roofs of the are the two little bathing-rooms, fitted up in an elegant rather horses, were introduced in great profusion. They covered their than a costly manner. At the other end is a second turret, in floors with cement, in which small pieces of marble or colonred which is a room that receives the rising and setting sun. Behind stones were regularly embedded in geometrical forms; and in this is a large repository, near to which is a gallery of curiositheir best rooms they used mosaic (inlaid work) with ornamented | ties, and underneath is a spacious dining-room. It looks upon margins and a device in the centre. The doors of their houses, the garden and the ride which surrounds the garden. Between being formed of wood, have been reduced to charcoal by the the garden and this ride is a banqueting-room. Two apart
ments run round the back of it, the windows of which look upon kind of architecture ; and there are some also in Germany and the entrance to the villa, and into a pleasant kitchen-garden. Italy. In the thirteenth century the Gothic style was used as From thence an enclosed portico extends, which, by its great much in private as in monumental or public architecture. In length, you might suppose erected for the use of the public. It the town of St. Yrieix there is a very fine house built in this has a range of windows on each side, but on that which looks style; and others are found at Montpazier, in the department of towards the sea they are double the number of those next the the Dordogne. Rural constructions, farms, and granges are garden. Before this portico lies a terrace, perfumed with violets. 'found at Meslay in Touraine, and near Coulommiers. Both in On the upper end of the terrace and portico stands a detached the fourteenth and fifteenth centuries wooden houses were com. building in the garden, which I call my favourite ; and, indeed, mon all over Europe. In the accompanying illustration is a it is particularly so, having been erected by myself. It contains representation of one of these, of which many specimens may be a very warm winter room, one side of which looks upon the seen in England. The storeys of these houses were executed in terrace, the other has a view of the sea, and both lie exposed corbel, that is, projecting one over the other—an arrangement to the sun. Through the folding-doors you see the opposite by which the upper rooms were enlarged, but which rendered chamber, and from the window is a prospect of the enclosed the lower storeys unwholesome, the light and the air being preportico. On that side next
vented from entering freely the sea, and opposite the mid.
into the rooms they contained. dle wall, stands a little ele.
This system of projecting gant recess, which, by means
storeys is proved to be of of glass doors and a curtain,
Oriental origin, from the ciris either laid open to the ad.
cumstance that it did not joining room or separated
make its appearance in from it. Adjoining to this is
Europe until after the time a bed-chamber, which neither
of the Crusades. This sys. the voice of the servants, nor
tem, which was proper in the murmuring of the sea,
the East, for defending the nor even the roaring of a tem.
lower part of the house from pest can reach.
the light and heat of the found tranquillity is occa
sun, was absurd in climates sioned by a passage which BUO
where these were always wel. separates the wall of the
comed as delightful visitors. chamber from the garden ;
After the thirteenth century and thus by that intervening
houses were constructed so space every noise is excluded.
that the gable-end of the Annexed to this is a small
roof fronted the street; and stove-room, which, by open
in the Middle Ages" to have ing a little window, warms
the gable to the street" inthe bed-chamber to the de
dicated the right of citizengree of heat required. Be
ship. Built without a reguyond this lie a chamber and
lar plan, these houses were, ante-chamber, which enjoy
owing to the arrangement of the sun, though obliquely,
the windows, both dark and from the time it rises till the
inconvenient within ; the afternoon."
stairs were constructed outThe houses of princes and
side, and in front of the the palaces of emperors occu
building; and in the recesses pied a great extent; and be
thus formed, turrets were sides baths, gymnasiums, and
built, which in the fifteenth gardens, they had sometimes
century were greatly multiattached to them a basilica,
plied, and added to their de a theatre, or a circus. Be.
Wooden façades fore the establishment of the
were generally more decoRoman dominion in Gaul,
rated than those constructed the inhabitants, according to
of stone; the posts, the beams, Vitruvius, lived in huts of a
and the panels were covered cylindrical form, covered with GABLED HOUSES OF THE THIRTEENTH CENTURY.
with a profusion of scalpshingle or thatch; and in Nor.
ture in wood; the roofs were mandy many vestiges of these are still to be found. The Romans decorated with elegant crests and graceful spires, surmounted gave to those people whom they conquered their religion, laws, with whimsical weather-vanes. During the Renaissance period. and customs; and the Gauls then built their houses like those the outward appearance of houses, as well as their internal of Rome. Numerous villas or country-houses, and rural en. accommodations, were greatly improved; the façades became gineering residences, were to be seen in Gaul; many of these more regular, and wood more rare; and when used, it was houses, as well as those built in towns, were constructed of wood mixed with brick and stone. From this period, sculptures placed on foundations of stone. Erected in a climate different , were spread over the fronts of houses with less profusion, and from that of Italy, the Gallo-Roman houses, especially in the with more taste. There are many specimens of houses built northern parts, were warmed by subterranean flues, called hypo. in the Renaissance style, in France, Germany, and Italy, as causts. During the first ages of the monarchy, houses in Gaul well as in England. The ancient towns of Rouen and Moret or France were made of wood, exactly similar to those of the in France, furnish some of the finest examples. From that time Roman period. In a description of the palace of Attila, given to the present day, private architecture has extensively inby the Byzantine historians, some valuable information is to be proved; the outward appearance of our houses has become less found on this subject. Some houses in stone, erected during fantastical, and the interior arrangements more convenient. the Roman period, are still to be found in France, with façades. Since the mediæval period the improvements in private edifices. very similar to those of modern erection. In the towns of the both in decoration and adaptation to the comfort of human life, south, and in the centre of France, such as Nismes, Perigueux, have been considerable; but the progress of domestic architec Metz, and Cluny, there remain some ancient specimens of this ture in England will be traced in future lessons.