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EXERCISE 45.

truly represent the actual rectangular axes which are employed 1. £947 6s. la. 9. 8962 bush, 16 qts. 13. 24645 cub.ft.930 in.

on the surface of the globe. The aspect they would then 10156 8 131442 1504

assume will be understood by reference to Fig. 6, where the 3. 16 tns. 16 cwt 23 lbs. 11950

1327148 1696 circle P MET PNQs may represent the first meridian, and the 4.403, 17

13143

24 14. 176 rt.ang.51°13'30" circle E O Q R the equator, their point of intersection E being 715. 10. 2068 qr. 5 bsh. 2 pk. 252 21° 45' 0" their origin as rectangular axes. We still call these rectangular 3. Gibs. 10 oz. 10 dwts.

39955° 4' 48"

axes, because the planes of the circles cut each other at right 6. 984 gals. 1 qt. 1 pt. 27204 qr 1 bsh. 2pk. 15. £174673 18s. 7.d. angles, and the sp 1erical angles PE O, PER on each side of the 11. 7821 2. 2 rods.

£195788 78, 3d.

meridian are right angles, whether taken from the upper or 7. 14778 ml.1 fur. 32 rd. 60162 80

16. 40 tn.6cwt.8lb.5oz. 451218

north pole P, or from the lower or south pole P; so that we 120

3667 12 84 7 12. 1199 yr.9m. 3w.ld. 4393 2 10 1

still have four right angles round the origin E ; but these are 8. Als.lm.4fur.30r. 2046 8 3 5 17. £14540116 18s. 3d. now spherical right angles, that is, angles formed by the quad2540 9 1 5 £16871008 98. 3d. rants or fourth parts of the circumferences of these great circles

of the sphere. In order to have a proper view of the rectangular EXERCISE 46.

axes on the sphere, we should require to be looking at the edge

or circumference of the circle PEPQ, and not at its plane or 1. £4 178.37.d. 5. 46 bush. 814 qts. yrs, d. hr. m. sec. £3 4s. 10d. 41 1211

surface as in the figure; then we should see the edge or circum

9. 10 35 1 13 111 £2 4s. 104d. 37 144

5 308 10 48 411 ference of the circle R E O Q cutting the former at right angles, 31 141

1 123 7 311 and both exhibiting at a distance the same appearance as the Ibs, oz. dwts. gr. 16 12%

40 8 32 34 lines xx' and yy' in Fig. 10. In this view, the point E being 5 104

3:7 10. 1° 48' 41}" the origin of the axes, all points on the surface of the sphere 6. 10 yds. 3 ft, 13 in. 1° 17' 38'

included between the semicircle EM PSQ and the semicircle 8 13 189 7. 9 yds. 1 qr. 0}} nls. 1° 0' 22"

E O Q, are said to be in north latitude and east longitude ; the 576 7 3!1 11. 10s. 11) 75d.

longitude" being measured from E along the eastern half of 3 10 151 211 12. 1511.

the equator EO Q, and the latitude from the same part of the 911 dys. hrs, min. sec.

13. 17H16

equator on a meridian passing through any of the points in 6,5 8. 24 8

40 14, 13571:. 7 14 43 20 15. 137900.

question and the two poles PP. All points on the surface 16. 30.

of the sphere included between the semicircle EMP8Q and 17. 219.

the semicircle ERQ, are said to be in north latitude and west longitude; the longitude being measured from E along the

western half of the equator ERQ, and the latitude from the LESSONS IN GEOGRAPHY.-XVIII. same part of the equator on a meridian passing through any of LATITUDE AND LONGITUDE-FIRST MERIDIAN, ETC.

the points in question and the two poles P P. All points on the

surface of the sphere included between the semicircle ETPNQ In the preceding view of the determination of the position of and the semicircle E R Q, are said to be in south latitude and a given point, we have not considered all the possible positions west longitude ; the longitude being measured from E along the of a point p round the point a, the origin of the co-ordinate western half of the equator E R Q, and the latitude from the ares. If these axes were produced in the preceding figures so same part of the equator on a meridian passing through any as to assume the appearance represented in Fig. 10, then, with of the points in question and the two poles P P. Lastly, all the same given distances or rectangular co-ordinates, there might points on the surface of the sphere included between the semibe four different positions of the point p with

circle ETPNQ and the semicircle EoQ, are said to be in reference to the rectangular axes x x' and

south latitude and east longitude; the longitude being measured TT, or the north and south straight line Y Y',

P. P.

from E along the eastern half of the equator E O Q, and the and the east and west straight line x x'. To

latitude from the same part of the equator on a meridian prevent confusion, therefore, and to fix the

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passing through any of the points in question and the two eract position of the point in question, it

P" poles PP.

P.'' might be agreed upon that every distance

Y

The student who reads the above explanation of latitude and measured from the origin A, along the portion

longitude on the rounded surface of the earth for the first time, of the axis ax, should be called east, and

Fig. 10,

may have a difficulty in realising the appearance of the sphere every distance measured from the origin A

from the diagram made on a flat surface, but he must endeavour along the portion of the axis a x' should be called west ; in like by his natural ideas of perspective to obtain as clear a notion as manner, that every distance measured upwards from the axis x x' he can. Of course the difficulty would be entirely removed by ekonld be called north, and every distance measured downwards the actual inspection of a globe; but, as it may not be possible from the axis x x should be called south. Moreover, it might for him to have a globe by his side while

he is reading this be agreed upon that every distance measured upwards from the lesson, we must try what we can do by means of the small azis xx shonld be called north latitude, and every distance Map of the World in the next page, although it must be rememmeasured doonwards from the axis x x' should be called south bered that the surface of no solid body as a whole can be truly latatude; and in like manner, that every distance measured represented on a plane surface such as the page referred to. from the point a to the right or eastward, should be called east with

that map before you, then, you will see the two sides of longitude

, and every distance measured from the point A to the the globe represented in what are called the eastern and western left of westward, should be called west longitude. Now this hemispheres. In order to see the whole of only one side, or half supposition is that which has actually been agreed upon ; 60 of the globe, the eye must be supposed to be at an infinite disthat in a map of the world upon Mercator's projection, as it is tance, and still possessing the power of sight ; accordingly, two called, the straight line Y Y' would represent the first meridian such sights directly opposite to each other will enable you to see or that of Greenrich; and the straight line x x' would represent the whole of the globe. This is the reason that two circles are the equator ; also, the point A would represent the point of necessary to represent the globe, because only one-half can be intersection of this meridian with the equator, which are in fact, seen at a time. If these two circles could be pasted along their the two rectangular

axes to which al points on the earth's edges or circumferences, back to back, so that their north and surface are referred, in order that their true positions (geo- south poles coincided, and then inflated till they assumed the graphical positions) may be determined. Accordingly, the point form of a globe, they would then form a pretty correct repreFig. 10) would be described as the position of a place in north sentation of the earth's surface. The equator, which you know latitude and east longitude ; the point p', that of a place in is a circle equally distant from the two poles, is represented on north latitude and west longitude; the point p", that of a place the Map of the World by a straight line drawn across the middle in south latitude and west longitude ; and the point P", that of of both hemispheres, marked by the word equator, and with a place in south latitude and east longitude.

degrees from 0° to 180° east, and from 0° to 180° west, reckoned If the straight lines x x', and yy', which we have supposed from the first meridian. to represent the first meridian and the equator, were to become In the map referred to, these degrees are marked only at the circumferences of circles of the same size, they would then more distance of every 20 degrees, on account of its smallness; in

A

larger maps they are marked at the distance of every 10 de- its intersection with the equator are marked 0, to show that grees; and in larger still, at less distances; the best being those latitude begins to be reckoned from these points. Each of the where they are marked at the distance of every single degree ; four quadrants (or fourth parts) of these circles is marked with but these, of course, must be of enormous size. The first degrees from 0° to 90° reckoned from the equator to the poles

. meridian, that of Greenwich, is known by its being marked In the map referred to, these degrees are marked only at the with 0 on the map or the equator. On looking at the eastern distance of every 10 degrees, on account of its smallness; in hemisphere, you will see this O marked on the equator, in the larger maps, they are marked at less distances; and the best Gulf of Guinea, south of the coast of Guinea in Africa; this is are those in which they are marked at the distance of every the origin of the rectangular co-ordinates, the first meridian, and single degree ; but these, of course, must be of very great size. the equator, and it is to this point that all measurements of In the same map, circles are made to pass through the correlongituule are to be referred. On running up the meridian, sponding points on the upper or northern quadrants of the outer passing through this zero point, towards the north pole, you will or surrounding circle of each hemisphere, and of the upper or find that it passes through London in the British Isles; this, northern half of the middle straight line extending from pole to you know, is not strictly the case, the meridian of St. Paul's pole, at the distance of every 10 degrees ; these upper quad. Cathedral, London, being about 6' or geographical miles west rants, and this upper half, actually denoting the northern porof the meridian of Greenwich; but this is so small in ordinary tions of meridians passing respectively through the points of maps, that it is scarcely perceptible, and certainly not mark- the equator marked longitude 20o W., longitude 1600 E., and able; whence the meridians of London and Greenwich are, for longitude 700 E. These circles, which on the globe are parallel common purposes, considered the same. The meridian of Green to the equator, are, from the nature of the projection employed in wich has been chosen as the first meridian, in preference to this map, not actually parallel to that line or to each other, being that of London, because Greenwich is the site of the Royal drawn from different centres; but they are still called parallels

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Observatory. Accordingly, all meridians which cross the equator of latitude, and are used to enable us to determine the latitude to the right of that of Greenwich, are said to be meridians of of any place on the map. Similar parallels of latitude are drama places in east longitude ; and all meridians which cross the through the corresponding points on the lower or southern quadequator to the left of that of Greenwich, are said to be meridians rants of the outer or surrounding circle of each hemisphere

, in of places in west longitude. For example: if you look at Peking, the same manner, and for the same purpose. For example: if in China, on this map, you will find that it lies to the right of you look at Peking, in China, on this map, you will see that it the first meridian in the northern half of the eastern hemisphere, lies between the equator and the north pole in the eastern hemi between two meridians which cross the equator, the one being sphere, and just upon the parallel of latitude marked 40° at each that which is, or should be, marked at the point of intersection side of the map: this enables you to guess that the latitude of 110°, and the other that which is, or should be, marked at the Pekin is nearly 40° north ; now the actual latitude is 39° 34' N. point of intersection 120°: this enables you to guess, by the Again, if you look at Buenos Ayres, in South America, on the vicinity of Peking to the latter meridian, that its longitude is same map, you will find that it lies between the equator and the about 116° east ; now the actual longitude is 116° 26' E. Again, south pole in the western hemisphere, and nearly in the middle if you look at Buenos Ayres, in South America, on the same between the parallels of latitude marked 30° and 40° at each map, you will find that it lies to the left of the first meridian in side of the map : this enables you to guess that the latitude of the southern half of the western hemisphere, between two meri- Buenos Ayres is nearly 35° south; now the actual latitude is dians which cross the equator, the one being that which is, or 34° 36' S. Having thus shown how to find separately the lati

. should be, marked at the point of intersection 50°, and the other tude and longitude of any place on the surface of the globe by that which is, or should be, marked at the point of intersection means of the circles and lines drawn in the Map of the World, 60°: this enables you to guess, by the vicinity of Buenos Ayres it is easy for

the student to combine these, and thus to deter: to the latter meridian, that its longitude is about 58° west; mine the actual position of any place on the surface of the now the actual longitude is 58° 25' W.

globe. Thus, we have fonnd that the city of Peking, in China, On the first meridian, the degrees of latitude are not marked; is situated in lat. 39° 54' N., and long. 116° 26' E.; and that the but the rked, in the Map of the World, on the circle city of Buenos Ayres is situated in lat. 34° 36' S., and long

hemisphere. On this circle, the points of | 58° 25' W.

[graphic]

COMPARATIVE ANATOMY.-IV.

our fields and adorn our gardens. We may take as a typical

representative of these animals, a genus called Campanularia. CELENTERATA : HYDROZOA.

The very name is similar to that given to a common garden The animals placed under this sub-kingdom exhibit their higher flower, the Campanula; and it is given to it for the same rank, not only in the distinctive character of possessing mem

Both have at the ends of their branches cup-shaped branes of definite structure, composed of or containing cells, organs, very much like bells. It is true that, in the animal, the which we have already remarked cuts them off from the Pro- bell, instead of hanging as a bell should, has its mouth upward;

reason,

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I., II. ECDENDRIUN RAMOSUM (HYDROZOON). III. HYDROZOON ENCRUSTING A SHELL (NATURAL SIZE). IV. RHOPALONEMA VELATUM, THE VEILED

CLUB-TENTACLED MEDUSA—A FREE SWIMMING MEDUSA. V. PERPENDICULAR SECTION OF A SEA ANEMONE. VI. TRANSVERSE SECTION OF ASEA ANEMONE. VII. PLEUROBRACHIA, A CTENOPHORE BELONGING TO THE ACTINOZOA. VIII. TRANSVERSE SECTION OF PLEUROBRACHIA

(CTENOPHORE). Refs. to Nog. in Figs. (I.) 1, feeding organs, with fringe of tentacles, mouth, and stomach (shaded) ; 2, flower-like organs of reproduction

which become detached and swim away, as in Fig. II. ; 3, creeping stem. (IV.) 1, polyp suspended within (2) the swimming-cup ; 3, its veil. (V.) 1, organs of reproduction on the edge of a septum ; 2, the face of a septum. (VI.) 1, the stomach wall ; 2, the body wall; 3. septa joining the walls. (VII., VIII.) 1, mouth; 2, centre of the stomach ; 3, comb-like locomotive organs ; 4, sack into which the tentaeles can be withdrawn; 5, tentacles cut short ; 6, nerve-knot and organ of sense.

tozoa, but also from the fact that in this class we find the first but in another respect the resemblance is better maintained, for indications of many of the structures which are necessary to, in the centre of the bell there rises thick club-sh body, and acquire such a great development in, the animals higher than which may well represent the clapper. The resemblance to a themselves. Definite membranes, muscular fibre, nervous and plant is maintained throughout the whole of the external form hepatic (liver) tissues are found in some of these animals. of this animal. With a creeping network of roots (if we may

A glance at any of the more common forms, such as are so call them), it encrusts some submarine rock, or stone, or shell, represented in Figs. I., II., III., will at once suggest that From this it sends up branching stems, each branch of which is these animals have a mode of growth and a general form very terminated either with a flower-like cup, which protects a tubular imilar to the higher forms of vegetables, such as grow in body with a mouth at its far end, surrounded with a circlet of

36

VOL. II.

feelers, or else with a fruit-like rounded organ, which, like a they contain. They then close around the prey, and press it in fruit, eventually drops off when fully developed. It is true that through the mouth into the interior, where its soft parts are if we were to attempt to guess at the functions of these organs dissolved, and its insoluble part is passed out again by the way from this analogy, we should find these appearances very decep it entered. tive. These creatures never derive any nutriment through their This short description leads as to remark upon the character roots or stems as plants do, but only through the little mouths which cuts off the Coelenterata from the higher animals. In the at the ends of the branches. Again, the flower-like heads are case mentioned, it will be noticed that the animal is, so to in function rather like leaves than flowers. Nevertheless, what speak, all stomach. The bounding wall of the stomach is also ever the function, the general plan of structure and growth is the wall of the body. In the higher animals the food carity is identical, and the likeness was so marked that naturalists were distinct from the body cavity. These higher animals consist of long before they would admit that these creatures were not a tube within a tube. The nutriment derived from food by plants. The animals whose branching stems are so exactly like them is strained through the walls of the inner tube, or otherto plants and shrubs, are microscopic; but this same resem- wise abstracted from it before it can be applied to the mainblance to vegetables is exhibited, though in a less striking form, tenance of the tissues of their bodies. In all the Calenterata, in the higher and larger members of the sub-kingdom. If the the food tube is not shut off from the cavity of the body. In the reader, while peering into the clear waters of a pool left by the hydra, the stomach is identical with the body cavity; in others, ebb of a spring tide, should see a rock covered by a multitude the stomach is continuous with the body cavity, being only parof flower-like heads, each with many circles of purple-tipped tially cut off from it by a circular valve, so that the stomach tentacles radiating from a common centre like the anthers of acts as a kind of porch or vestibule to detain the food a short the wild rose or the buttercup, all of which seem to float and time, and it is then passed on into the lower part of a tube of sway passively with each little eddy he excited, he would cer- equal dimensions. In others, the central stomach divides into tainly take them for sea flowers. Even the common actinia, radiating hollows, and these divide and subdivide, and often prawhich is left dry on the rock, collapsed into a dome of jelly, duce a network of fine canals. In these the stomach presents might readily be taken for a flower when, at the first approach the structure, and has also the office of both stomach and of the sea, it expands from this bud-like condition into a spread. blood system of higher animals. All the animals which have ing disc, fringed not only with tentacles, but with a circular row stomachs such as we have described, belong to the subof bright blue knobs.

division of the Coelenterata called Hydrozoa. The other subOtherwise well-educated men, who know nothing of the division, called Actinozoa, presents a different arrangement. natural sciences and the number of these is large), often With them, although the stomach freely communicates with the declare that the lowest animal is but little removed from the body cavity, it is not identical with it, and cannot be said to be highest plant. This, however, is a popular error, and the continuous with it. Indeed, these animals show an approach reverse of this is the case. The true statement is that both to a higher grade by having a stomach within the body wall; kingdoms start from the same point. The simplest and but this tube within a tube is not a perfect one, but opens lowest forms of both, especially in their immature condition, below into the general cavity of the body. Also & number of are almost identical. At this simplest and earliest stage of partitions run from the body wall to the stomach, so as to development, the plant makes quite as decided an approach maintain the latter in its position, and to divide the body towards the typical life of an animal as does the animal make cavity into compartments. This arrangement is well seen in a counter-approach towards the typical life of a vegetable. Figs. V. and VI. The young spore of a conferva (vegetable) is locomotive, and To return to the Hydrozoa. The simple hydra is a locomotive moves by the same mechanism as a protozoon. Thus the tube, but it fixes itself by one end in a temporary manner. This animal and vegetable kingdoms not only meet at their lowest animal produces young not only from eggs in the ordinary way, point, but the vegetable, so to speak, travels more than half but also by putting forth buds from its sides, which, while way to effect the meeting. From this common point of contact attached to the parent, develop mouths and arms, and then the two kingdoms slowly diverge from one another; but the become separated, being able to live for themselves. divergence is so gradual, the angle of divergence is so small, The hydru, therefore, exhibits functions and tendencies which, that for some distance they move in an almost parallel course. when carried to a greater extent in other species, produce very Now, as the vegetable stops far short of the development many modifications, and these may be grouped under two type, of the animal kingdom, we must look for the parallel to its which, though apparently very different, are, as we shall set, higher forms, not in the lowest animals of all, but in those closely connected with one another. at some little distance up the scale; not in the last and 1st, the fixed and branched hydrozoa, with long branching lowest division, Protozoa, but in the penultimate sub-kingdom, stem, each of whose heads is very like the hydra; and 2nd, thơ Coelenterata. It must, however, be remembered that the free swimming hydrozoa, which float at large in the ocean, and analogy to plants is only a parallel. There are no intermediate have locomotivo organs to raise them to the surface and propel forms connecting the most plant-like hydrozoon with the most them along. coral-like plant. To find the links of the chain of life which The animals which range themselves round the first of these connects them, we must run downward throngh all the grades types are the most perfect examples of the vegetative habit

. of animal life, to mount up again by the different grades of The home of the

Coelenterata is the water, and almost all except vegetable development. We shall find that though there are the hydra live exclusively in the salt waters of the ocean. These fundamental differences, yet the analogy is very strict between fixed hydrozoa, of course, need not only an atmosphere of water, Calenterata and plants in very many respects.

but a bottom whereon to grow. They are to be found around Though unlimited growth and repetition of parts be the main our coasts, some of them in the pools left by the retreating characteristic

of both Coelenterata and the higher plants, some tide between high and low-water mark. The dredge has brought of the former are simple enough. Just as the little pasch- up some of these animals from great depths, and it is probable flower (Anemone pulsatilla) sends up its one blossom in the that they flourish at still lower levels; but it is unlikely that grass, so does the little fresh-water hydra extend its few they could live under the enormous pressure exerted by the OFER tentacles around the mouth end of its tubular body, while lying waters in the profundity of mid-ocean. Most of these plantit attaches itself, by the other end of the tube, to a water-weed. like compound animals are invested with a horny sheath which

This animal is simply a tube or bag, while its tentacles are covers the stem and branches, so that the beautiful patterns in narrower tubes, whose hollows communicate with the main which they grow may be preserved after the soft parts of the one. These are arranged in a circle round the mouth, which is animal have been dried up. A collection of such dried specimena a perforation in the free end of the tube. The bag flexible, gives a far better idea of the animals than a dry herbarium and composed of two layers of tissue closely adhering to one gives of the different species of plants; for the hard parts being another. The stuff of wbich the bag is made is double, and of a stiffer nature, and external instead of internal, the outer the lining is so like the outer stuff, that the bag can be turned form is far better preserved.

Some of these hard sheaths of inside out, as Baron Munchansen served the wolf, without skeletons have at the end of each branchlet a little cap which, in deranging its economy. The long arms sway about in search of the living state of the animal, defends the little hydra-like polvo food. Any little animal unfortunate enough to come in con- pite (as it is called). In another order the sheath ends abruptly, tact with them, becomes benumbed by some stinging organs allowing the polypite to be protruded nakedly beyond it.

The animals represented by the other type are far more inde- cup. These are called Medusæ, from Medusa, whom Neptune pendent. They need no sea-bottom, and are not confined to the loved for her golden locks, which were afterwards converted into coast, but swim freely in the sea far from any land. The headed snakes. Whether the large round disc-like bodies of these naturalist who during a sea-voyage has energy enough to con- creatures, which every one must have seen who has been by the struct a surface-net and trail it from the vessel's stern in fine seaside, best represent the Gorgon before or after the transformacalm weather, is sure to be rewarded by obtaining many of these tion, must be left to the imagination of each individual. These animals. They, however, of course, collapse when removed from creatures are also remarkable because they present the first their element, and have to be re-immersed in a pail of water be- indications of those organs of sense which become so com. fore they exhibit their beautiful structure. We have said these plicated in higher animals. Around the margin of the cup or animals swim in mid-ocean; but how do they swim? They bell of some Medusæ, sometimes situated just opposite each swim by means of two different kinds of organs, one active and tentacle, and sometimes between these, sometimes protected by the other passive. One order is possessed of a float or bladder a kind of flap and exposed nakedly on a slight projection, which holds air, so that by means of this they can be kept near are found a number of little roundish bodies. These generally the surface while attached to their float, and hanging down from consist of a little vesicle with a nerve ending behind it, and a it either directly or by the intervention of a long living rope, spot of bright-coloured pigment behind this again. Other of the polypites extend themselves in order to be ready to devour these bodies enclose in a vesicle a little crystal of carbonate of any small prey with which they or their tentacles come in contact, lime. It is thought that the first are adapted to receive imas the whole system is drifted by wind and current along the pressions of light; and the last, vibrations of sound. In fact, they surface. Other free-swimming hydrozoa have, in addition to or are the simplest eyes and ears known in the animal kingdom. in lieu of floats, flexible and contractile cups, to the outside of Another order of the hydrozoa are like the simple hydra in which the strings of polypites are slung. These cups the that they have a disc by which they can fix themselves in a animal causes to be suddenly contracted by bringing the sides of temporary way, but they differ from these animals in that they the cup forcibly together, and so driving out the water. This possess an organ expanded round the polypite, called an umbrella. motion causes the cup to be driven in the direction towards This organ they can use as a swimming organ when they detach which the bottom of the cup is turned, and so to drag after it themselves. the chain of polypites. The cup is then allowed slowly to dilate Thus the Hydrozoa have been divided into seven orders, thus by the elasticity of its substance, and is then again forcibly defined :contracted. It may be conjectured that these swimming organs, 1. Hydridæ.–Animals characterised by a single locomotive though they have a locomotive function, are not used to effect polypite. locomotion in any definite direction, except it be upward or 2. Corynidæ.-Animals, simple or compound, which are fixed, downward. No doubt, the instinct of these creatures, low as it and have no cups developed from the hard outer layer to protect iz, induces them to seek the surface in fine calm weather, and to the polypites. sink to stiller depths when rain and storms come. These again 3. Sertularidæ.-Compound animals, with protective cups to may also be used to effect change of place when the waters are their polypites. stagnant; but, of course, the animals so moved do not pursue 4. Calycophoride (Cup-bearers). — Free-swimming animals, their prey. Trailing as a car from its balloon, these creatures with an undivided string of polypites slung to the outside of tre floated through the ocean and find their food haphazard. one or more swimming cups. The question arises, how do these soft and feeble creatures secure 5. Physophoridæ (Float-bearers).-Like the last, but having live things which have much greater power of locomotion than floats. themselves, and whose struggles, one would think, would be suffi- 6. Medusidæ.--Animals with a single polypite hanging from cient to tear the delicate arms of their captors quite away? Their the centre of a large cup-like disc. power of capture is rather chemical than mechanical. All the 7. Lucernaridæ.

Animals characterised by an umbrella. Coelenterata have small organs embedded in their tissues near These would seem at first sight to be good marked characters, the surface, called thread-cells. They are especially numerous in by which to distinguish the orders ; but in reality these orders the tentacles, and consist of small double-walled sacs. The outer are only provisional, and their unsatisfactory character will illusBac bursts under the slightest excitement or touch, and a long trate how futile it is to endeavour to classify animals before we fine thread, which lay coiled up between the two sacs, and is know their whole life-history. It is found that some of the attached to the end of the inner sac, is darted forth with a flower-like heads of the orders 2 and 3 become developed into rapid motion. This thread is a sting which conducts poison animals precisely like those belonging to the order 6, and then into the body of the animal it touches; but whether the poison drop off and swim away as complete Medusæ. Further, some is contained in the inner sac, and is passed up through the of the order No. 7, which swim freely, give birth to young that thread, or whether it lies between the sacs, does not seem to be become permanently fixed, and grow for some time like animals ascertained. Whatever the method, the fact of the stinging of the second and third order. The circle of life, however, is sensation produced by the thread-cell is demonstrable enough. completed in both cases, for the free-swimming Medusæ have Not only are the little animals which come in contact with the young which grow into compound animals, like the stock from arms of the hydrozoa seen to become benumbed and helpless, which they were derived, and the fixed young of the Lucernaridæ, bat even upon man the stinging is sometimes severe. One of when exposed to fresh or unfavourable conditions, have their the largest of the float-bearing hydrozoa, which is a very con- tubular bodies transversely divided into a number of saucerEpicnous object at sea, not only from its comparatively large shaped discs, which one by one become detached, and swim size, but also from the beauty of the rainbow tints which shine away to become developed into an umbrella-bearing Lucernarid. forth from its float, is called the Portuguese man-of-war. This The phenomenon above described is called an "alternation of animal furnishes the rough-and-ready seaman with a means of generations,” but the phrase is an objectionable one. gratifying his taste for practical jokes. The Portuguese man. In the engraving, two forms (Figs. VII., VIII.) taken from of-war is put in a pail, and the novice is induced to touch it, the other class, which is called Actinozoa, are given, in order when he not only becomes the victim of the discharge from the to show the contrast between them and the Hydrozoa ; but we man-of-war, but also of a broadside of laughter from the crew must leave the description of them for another lesson. of his own vessel. Aristotle was so well acquainted with the stinging power of these animals, that he called them Acalephæ (or vettles).

READING AND ELOCUTION.-XVIII. There is another order of free-swimming hydrozoa, which

ANALYSIS OF THE VOICE-(continued). differ from those described in that their swimming cup is single, and instead of having the living rope with its polypites and

EXPRESSIVE TONES (continued). tentaeles slung on to its outside, has a single polypite suspended Rule 4.--Awe has usually a suppressed” force, a very from the centre of its under or concave side, while the tentacles low” note, and a very slow” movement. Solemnity, reverare arranged at regular intervals round the margin of the cup. ence, and sublimity have a “moderate" force, a "low" note, The mouth of the polypite leads into a central stomach, which and a "slow movement.” All four of these emotions are sendy out radial canals to run to the margin, and these are there uttered with “effusive medial stress," and deep, but “

- pure connected with a circular canal, which runs round the lip of the “ pectoral quality ;” together with a prevalent monotone."

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