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LESSONS IN GEOGRAPHY.-XVI. tity by a number, if we multiply separately the parts of which the quantity is composed, and then add the products together, HAVING explained, in a previous Lesson (see Vol. II., page 4), the result is the same as would be obtained by multiplying the the nature of the seasons arising from the annual motion of the whole quantity by that number. The above operation would, in earth in its orbit or path round the sun, and the parallelism of practice, be thus arranged

its axis, or the invariable inclination of that axis to the plane of £5 29. 7.

its orbít, we shall render this subject more strikingly evident by 78.

means of the accompanying diagram of the seasons. Here the

sun is considered to be fixed at the point F in Fig. 4 (page 80), £30 15s. 10.d.

which is considered to be the focus of the elliptical or oval orbit Hence we see the truth of the following

in which the earth moves, and which is so near to the centre of 9. Rule for Compound Multiplication.

the curve that it may be, on this small scale of figure, reckoned Multiply each denomination separately, beginning with the the same with that centre; and you know that the centre is lowest, and divide each product by that number which it takes the point where the major axis, between summer and winter, of the denomination multiplied to make one of the next higher. intersects or crosses the minor axis, between spring and autumn. Set down the remainder, and carry the quotient to the next If you are curious enough to know how far the focus, F, is from product, as in addition of compound numbers.

the real centre of the orbit, we shall tell you ; it is about oneObs.—Ang multiplier is of necessity an abstract number. sixtieth part of the half of the major axis, or of the mean disTwo concrete quantities cannot be multiplied together. Multi-tance between the earth and the sun, from the real centre. Let plication implies the repetition of some quantity a certain us see if we can express this distance in some known measure. number of times; and we see, therefore, that to talk of multiply. The mean distance of the earth from the sun, or the length of ing one concrete quantity by another is nonsense.

the mean semi-diameter of the earth's orbit, is about 23,109 In the case of geometrical magnitudes—in finding the area of times the length of the mean terrestrial radius, or of the mean a rectangle, for instance—we do not multiply the feet in one side distance from the centre of the globe of the earth to its surface. by those in the other, but we multiply the number of feet in ono

The earth's mean radius is 3,956) British miles, its mean diaside by the number of feet in the other, and from geometrical meter being 7,913 miles. Therefore multiplying 3,9564 miles by considerations we are able to show that this process will give us 23,109, we have the mean distance of the earth from the sun, the number of square feet which the rectangle contains. The that is, half the major axis of its orbit, about 91,431,000 in very idea of multiplication implies that the multiplier must be round numbers. This makes the mean diameter of the earth's an abstract number. It is of the nature of twice, thrice, etc. orbit about 182,862,000 miles, and its approximate circum(Vide Obs. of Art. 7, Lesson XXII., Vol. I., page 380.)

ference about 574,709,000 miles. The linear eccentricity of the

carth's orbit being :0168, or about one-sixtieth of its semi-axis 10. ADDITIONAL EXAMPLE IN COMPOUND MULTIPLICATION. major, or mean distance of 91,431,000 miles, we have 1,523,850 Multiply 12 lbs. 3 oz. 16 dwts. by 56.

miles for the distance between the centre of the orbit and the In a case like this, where the multiplier exceeds 12, it is centre of the sun, or the focus of that orbit. Consequently, often more convenient to separate it into factors, and to mul- the earth is about double this distance, or 3,047,700 miles nearer tiply the compound quantity successively by them (Lesson VI., to the sun in winter than in summer. Art. 2, Vol. I., page 95). Now 56 = 7 X 8.

In Fig. 4, the earth is represented in four different positions Ibe. oz. dwts,

(momentary positions) in its orbit; namely, at mid-summer, mida spring, mid-winter, and mid-autumn. In all these positions, as well as all round in its various positions in the orbit, the parallelism of its axis, N 8, is preserved. This axis is inclined to the plane of the orbit, as we have before observed, at an angle of 66° 32'; hence it makes an angle of 23° 28' with the perpen

dicular to the plane of its orbit; for the perpendicular, repre16 Answer.

sented by the dotted line passing through the centre, o, makes EXERCISE 45.

an angle of 900 with the plane of the orbit; and subtracting Work the following examples in compound multiplication :

66° 32' from 90° gives the remainder 23° 28', which is the angle

between the axis, N s, and the perpendicular, or dotted line. By 1. £35 68. 7d. by 7.

reason of tiris parallelism of the axis N s, it so happens that at 2. £1 69. 8 d. by 18. 3. 1 ton 2703 lbs. by 15.

mid-spring, or March 20th, the half of the globe is illuminated 4. 16 tons 3 cwt. 104 lbs. by 25 and 84.

from pole to pole, that is, from the northern extremity of the 5. 17 dwts. 4. grs. by 96.

axis N, to the southern extremity of the axis S, and the days 6. 15 gals. 2 qts. 1 pt. by 63 and 126.

and nights are then exactly equal all over the earth; that is, 7. 175 miles 7 fur. 18 rods by 84, 196, and 96.

there are twelve hours of light and twelve hours of dark. 8. 40 leagues 2 m. 5 fur. 15 r. by 50, 200, and 385.

ness to every spot on the earth's surface for this day. Hence 9. 149 bush. 12 qts. by 60, 70, 80, and 90.

this day is called the equinox (equal night) of spring, or the 10. 26 qrs. 7 bush. 3 pks. 5 qts. by 110 and 1008.

vernal equinox. Again, at mid-summer, or June 21st, the half 11. 150 acres 65 rods by 52, 400, and 3000.

of the globe is illuminated from the circumference of a small 12. 70 yrs. 6 mo, 3 wks. 5 d. by 17, 29, and 36. 18. 205 cubic ft. 10 in. by 93, 496, and 5008.

circle of the globe at the distance of 23° 28' from the north 14, 75° 40' 21" by 210, 300, and 528.

pole, n, to the circumference of a small circle at the distance of 15. £213 5s. 6 d. by 819 and by 918.

23° 28' from the south pole, s; and the day is twenty-four hours 16, 5 tons 15 cwt. 17 lbs. 3 oz. by 7, by 637, and 763.

long at all places of the earth contained in the space between 17. 213 78. 9fd. by 1086012 and by 1260108.

the small circle and the north pole; that is, there are twenty(For the last three questions refer to Lesson VII., Arts. 15, 16, four hours of light and no darkness at all to every spot within Vol. I., page 111.)

this space on this day ; but the night is twenty-four hours long

at all places of the earth contained in the space between the KEY TO EXERCISE 43, LESSON XXV. (Vol. II., page 37). small circle and the south pole, that is, there are twenty-four

9. 109 leagues 2 miles 15. 2 oz. 3 drachm 12 hours of darkness and no light at all to every spot within this 6 fur. 1 foot.

grains.

space on this day. As at this point the earth begins to return 10. 468 acres 1 rood 6 p. 16. 1203 cubic yards 6 to a position similar to that at the vernal equinox, and the sun 11. 43 sq. yds. 5 sq. ft. feet 1059 inches. seems to be stationary as to its appearance and effects on the

125 sq. in. 17. 9 square miles 86 earth's surface for two or three days before and after this day, 6. 9 tons 8 cwt. 5. 12. 240 gallons,

acres 1 rd. 35 p; it is called the summer solstice (sun-standing), or the tropic Ibs.

13. 115 weeks 15 hours 18. 22 Fr. e. 4,9r. 2 no(turning) of summer. Next, at mid-autumn, or Sept. 23rd, the 7. 45 tong 4 cwt. 45 25 minutes. 19. 11 cong. 7 o 16 13 14, 71 years 5 months

5f3 6 m.

half of the globe is again illuminated from pole to pole, and the 8. 107 lbs. 7 oz. 8 dwte.

1 week 4 days 11 20, 22 loads 1 quarter same appearances take place as at the equinox of the spring, 11 grains. hours 7 min,

3 bushels 2 pecks. that is, the days and nights are then exactly equal all over the

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1. £18 39. 4 d. 2. £102 38. 5 d. 3. £93 Os. 28.d. 4. £4345 2s. 07d. 5. £57613 25. 6a.

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SPRING.

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SUMMER.

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AUTUMN.

earth, or there are twelve hours of light and twelve hours of would pass through c, the centre of the sphere. Every circle, darkness to every spot on the earth's surface for this day. whose plane thus passes through the centre of the sphere, is Hence this day is called the equinox of autumn, or the autumnal called a great circle of the sphere. It is further evident that equinox. Lastly, at mid-winter, or Dec. 21st, the half of the every point, such as M, on the surface of the sphere, will describe globe is illuminated from the circumference of a small circle of a circle smaller than the circle EQ in proportion to its distance the globe at the distance of 23° 28' from the south pole, 8, to from the point E on either side, or to its vicinity to either of the the circumference of a small circle at the distance of 23° 28' points P P; and that if the sphere were cut by a plane or flat from the north pole, n, and the day is twenty-four hours long surface, like an orange by a knife, through such a circle as x , at all places of the earth contained in the space between the it would not pass though c, the centre of the sphere. Every small circle and the south pole ; that is, there are twenty-four circle whose plane does not pass through the centre of the hours of light and no darkness at all to every spot within sphere, is called a small circle of the sphere. Accordingly, the this space

circles M 8 and on this day ;

TN are called but the night

MARCH 20.

small circles of is twenty-four

the sphere; and hours long at

if the points all places of the

M and be earth contained

equally distant in the space

from the point between the

E, these circles small circleand

will be equal in the north pole;

size, and their that is, there

planes will

WINTER. are twenty

cut the axis four hours

DECEMBER 21.

in two points of

JUNE 21. darkness

equally disand no light

tant from the at all to every

centre, c. The spot within

plane of a great this space on

circle, such this day.

E, cuts In looking

the globe or at the dia.

sphere into two gram, you see

SEPTEMBER 23.

equal

hemi at the equinox

spheres; but of spring, or

the plane of March 20th, FIG. 4.—DIAGRAM SHOWING THE CHANGES OF THE SEASONA.

a small circle the whole of

cuts it into two the illuminated half of the globe, because from the represen- | unequal parts, or segments (cuttings) of a sphere. For some purtation of its position it is turned in front both to the sun at F, poses, the circumference of a circle, large or small, is divided and to you the spectator; at the summer solstice, or June 21st, into 360 equal parts, in order to enable us to measure distances you see only half of the illuminated half of the globe, because along the circumference; each of these equal parts being it is turned in front to the sun at F, but only sideways to you called a degree ; for other purposes, the circle is divided into the spectator, you being outside of the orbit; at the autumnal two equal parts called semicircles, and these are also divided equinox, or Sept. 23rd, you see none of the illuminated half into degrees, each containing 180 degrees, and both 360 of the globe, because it is turned in front to the sun at F, but | degrees as before ; and for other purposes still, the circle is at the back to you, the spectator, you being

divided into four equal parts called quadoutside the orbit and as it were behind the

P

rants, each containing 90 degrees, and the globe; and at the winter solstice, or Dec.

whole containing 360 degrees as before. 21st, you again see half of the illuminated

Each degree is divided into 60 equal half of the globe, because it is turned in

parts called minutes, and these minutes front to the sun at F, but only sideways to M

S

(minute parts) are employed to express you, the spectator, for the same reason as

R

any part or fraction of a degree which may before. But were you placed in the middle

be found over and above a certain number of the orbit at the point F, you would,

Q of degrees in any distance.
E

Again, each by turning round and round to the different

minute is divided into 60 equal parts called points of it we have been describing, see the

seconds, and these seconds (second minuto whole of the illuminated half of the globe at

o

parts) are employed to express any part each point; and were you placed outside of

or fraction of a minute which may be found the orbit in the directions of the major and

T

N

over and above a certain number of degrees minor axes, and made to look at the globe in

and minutes in any distance ; and so on, these directions only, you would see none of

to thirds, fourths, eto. This division of the the illuminated half of the globe, but only

degree is called the sexagesimal (by sixtieths) the dark side in each position.

P

division of the degree; the division of We must now explain the nature of some

FIG. 5.

the quadrant of a circle into 90 degrees is of the more important circles on the sphere

called the nonagesimal (by ninetieths) division or globe of the earth. If in Fig. 5, which we suppose to be a re- of the quadrant. The French, in some of their scientific works. presentation of the globe of the earth, P p denotes the axis—that adopt à different division of the circle and its parts. They is, the diameter of the sphere, passing through the centre, c, on divide the circle into 400 equal parts, calling them degrees ; and which the sphere or globe revolves like a wheel on an axle—then of course, the quadrant into 100 degrees ; also the degree into it is evident that every point on its surface will, in the course of 100 parts called minutes; and so on : this is called the conte. its revolution or whirling on its axis, describe a circle. Thus the simal (by hundredths) division of the quadrant. Any pamber of points, M, E, and r on the surface, will describe the circles M s, degrees is marked by a small circle placed on the right of the EQ, and T n respectively; and it is evident that the point e, number in a small character, and above the line; thus 270 equally distant from the two points P p, the extremities or poles denotes 27 degrees. Any number of minutes is marked by one of the axis, will describe the largest circle of all in the course of dash from right to left, on the right of the number; of seconde, the

revolution ; and that if the sphere were cut by a plane or flat by two dashes, and so on; thus 10 denotes 10 minutes, 10% anrface, like an orange by a knife, through the circle E q, it | denotes 10 seconds, etc.

Cuvier divided the animal kingdom into four sub-kingdoms, COMPARATIVE ANATOMY.-II.

as follows:

Vertebrata, DIVISIONS OF THE ANIMAL KINGDOM-VERTEBRATA-MOL

Mollusca,

Articulata, LUSCA-MOLLUSCOIDA-ANNULOBA - ANNULOIDA-CELEN

Radiata. TERATA-PROTOZOA.

The three higher divisions remain very much as he constituted The main divisions of the animal kingdom, called sub-kingdoms them. There could be no higher testimony to the value of these or branches, were first established on anything approaching than this, that all the multitude of higher animals that have & scientific basis by the great Baron von Cuvier. Previous been discovered or examined since his time fall naturally under classifiers had endeavoured to mark out these divisions by one or other of his divisions. Cuvier himself assigned some differences in some one organ or system of organs. The system animals to the wrong branch, yet when the error was discovered which was generally made use of, as producing the most natural it did not necessitate the formation of a new system, but merely classification, was that of the organs of circulation of the blood, a transferenc from one branch to another; and this proves conor the nutritive fluid which answered to the blood. The classifi- clusively that the classification was not an artificial system cation of animals according to the structure of their hearts, fitted on to his knowledge, which, though wide, was of course blood-vessels, etc., was perhaps as good as any founded on any limited, but was a recognition of the fundamental plan of one system of organs. At least, our great anatomist, Hunter, nature.

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I. SKETCH OF HADDOCE, SHOWING ITS EXTERNAL PORM, AND ALSO THE ARRANGEMENT OF ITS INTERNAL ORGANS. II. TRANSVERSE SECTION OF

HADDOCK AS EXHIBITED AT THE LINE a b. III. SKETCH OF LOBSTER, SHOWING ITS EXTERNAL FORM AND THE ARRANGEMENT OF ITS

INTERXAL ORGANS. IV. TRANSVERSE SECTION OF LOBSTER, EIHIBITED AT THE LINE a b. Rets. to Nog. in Figs. I., II., III., IV.-1, heart; 2, nervous system ; 3, brain; 4. alimentary canal; 5, vertebral column ; 6, sympathetic

nervous system. who had carefully examined all the systems of organs of animals The lowest of these branches, designated Radiata, has not in relation to their use in classifying, thought so. It now, how maintained its ground as the others have, for the following ever, seems to be laid down as a rule that it will not do to rely reasons. Many of the animals assigned to this branch are on any one character in classification. If a classification be microscopic, and had been but little examined, and Cuvier made in dependence on the modifications of but one organ, it is founded his branch on the plan of structure exhibited by some sure to be an unnatural one. If, on the contrary, it can be of the more conspicuous animals, such as the star-fish, and he stated that any group of animals is distinguished from the rest assumed that all the lower animals conformed to that plan of by peculiarities in two or more systems of organs, that group is structure. This, however, has been found not to be the fact. sure to be a natural one. Cuvier was more successful than his Nor was the definition of this branch good as far as it went, predecessors, not so much because he had any better key by since it was founded on one peculiarity alone, namely, the plan which to interpret the animal kingdom, as because he relied on of structure. In fact, however derogatory the admission may Do key, but trusting to his wide knowledge of the structure of be to the great anatomist, we are compelled to admit that his animals

, and to his sagacious perception of what similitudes or sub-kingdom Radiata stands in the same relation to the rest of differences were fondamental and what were unimportant, he his admirable system, as the untidy lumber-room—which genemade a classification which recognised the plan of structure of rally exists in even a well-ordered house, and into which every. each animal as a whole, that is, as made up of the sum of its thing which has no definite place of its own is thrown—does to organs. The difficulties attending such a method are far greater, the rest of the establishment. Most of us who make natural the definitions of the branches thus formed are less simple and history collections of any kind, have in our cabinets a spare precise, than those of the former methods, but the results drawer, into which specimens we have not had time to examine have the merit of being true to nature, and therefore stable. or to dame, or whose place in the collection we are donbtful

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about, are placed. The contents of such a drawer are the tubes, and which are wielded from within. Further, there is measure of our ignorance, and when we are particularly fresh manifest tendency for each segment of the body to have a pair in spirit, or have much leisure, we open it with a confident of limbs. Thus, beginning from behind, we find on the last expectation that a patient study of its contents will lead us to a segment the limbs are not developed, but only indicated; but further knowledge, and a truer and more complete arrangement. on the next they form the side lobes of the tail, and are the main Such a drawer is Cuvier's branch Radiata, and men who have felt instruments by which the lobster darts rapidly backward when that Cuvier had forestalled all other anatomists in the arrange- alarmed. The next four segments have each paired limbs, conment of the higher animals into their main divisions, have been sisting of two small fringed plates set at the end of a joint, and able to solace themselves by re-arranging the heterogeneous with them the lobster paddles quietly forward. Then comes & number of animals for which the star-fish and sea-urchin stood segment with a pair of limbs composed of two joints, used for as the representatives in the mind of Cuvier.

other necessary purposes. Then under the great shield are the Inasmuch as we must dismiss this branch Radiata from our walking limbs, all many-jointed. Two pairs with one claw are system, and shall not be able to recur to it again, as we must preceded by two more terminated by small pincers; then come to the other branches, it is, perhaps, as well that we should the formidable claws. Next come the foot-jaws and jaws. explain the character on which it was founded. Cuvier observed There are six pairs of these, placed closely one over the other, that while some of the higher animals have their two sides alike, beneath the mouth; they cannot be seen in the engraving. yet they could be split down the middle in one direction only, so Then come the pair of longer feelers, the shorter feelers, and as to leave two exactly similar halves. Thus, if one of us were finally the jointed eye-stalks. Thus each of the twenty-one segdivided from the crown of the head vertically downward, so ments of which the lobster's integument is supposed to consist that the division passed through the mid-line of the back and has a pair of well-developed limbs, with the exception of the also of the breast, we should be divided into two like halves; last. but if the vertical division were made in any other direction, the How utterly different is the locomotive apparatus of the fish ! two halves; though they might be equal, would certainly be not The necessary hard parts upon which the muscles must play are alike. If, on the other hand, a star-fish be placed flat on a nowhere to be found on the outside. They are situated intertable, it may be bisected in more than one direction, and the nally. Running through the centre of the body from snout to halves would be alike. Indeed, if we wanted to divide it into tail is a bony column or axis. This axis consists of pieces like portions, we should naturally cut it into five or ten or more which are so closely united end to end that they support one segments, beginning from the centre, and cutting outwards. The another, but are capable of a slight motion on one another, 80 organs are not paired on each side of one plane, but arranged that the back-bone which they form can be bent and slightly like the spokes of a wheel in diverging directions from a central twisted. This back-bone, ending forward in the base of the axis. This plan of structure was therefore considered as the skull, is the main part of the hard skeleton which affords attachtype of the branch Radiata, a radius meaning a line drawn from ment to the muscles which move the limbs. In this case the the centre to the circumference of a circle. If this radial tendency of each segment of the internal skeleton to produce arrangement of organs had been universal throughout this sub- limbs is so little marked, that there are not more than two kingdom, and were found in no other, this would have formed a pairs of paired limbs in all; and throughout this large subwell-marked division, but it is not so. Some of the organs of kingdom, which includes brutes, birds, reptiles, and fish, there higher animals have an apparent radial arrangement, as, for are never more than this number found, though sometimes there instance, the hooklets by which intestinal worms fix themselves. is but one pair, and sometimes none at all. These limbs are not In so-called radiate animals there is generally a two-sided jointed hard tubes, pulled and moved by muscles running up the arrangement to be found. Thus, while the arms of the sea inside of them, but they are supported by bony levers, while the anemono are radial, stretching away on all sides, its mouth has muscles act on them externally. two lips and two corners. The common purple-tipped sea- Passing on to the other systems of internal organs, we find a hedgehog (echinus) is in outward form a typical radiate, but its marked difference in the arrangement of the nervous, alimentary near ally, the heart-archin, is almost as two-sided as ourselves. (food), and blood circulatory systems, in relation to one other. We therefore reject this sub-kingdom, and substitute others in In the lobster the nervous system consists of a double series its stead, as will be seen in the sequel.

of rounded masses called ganglions, which commence with two Instead of at once enumerating the numbers of sub-kingdoms lying side by side (though partially united together) above the of the animal kingdom, and appending to each a dry catalogue mouth, and in connection with the eyes, antennæ (feelers), eto. of the characters upon which they are formed, it is, perhaps, From these two cords stretch back, one running on each side better to induce the reader to examine two animals belonging to the mouth or throat, to another double ganglion, and from this two different branches for himself, so that he may remark the cords pass back which unite the remaining nervous masses togeessential differences in structure which they manifest. Suppose, ther, all of which lie in a series along the floor of the tubular then, he procure a prawn and a stickleback, or, if he aim at cavity of the body enclosed by the rings. Each ring has a double larger specimens, more easily examined, he can obtain, as we ganglion of its own, but these are sometimes united together, as have done, a lobster and a haddock. If these be carefully in the lobster. The food canal runs from end to end through observed, first as to their external character, and then as to the centre of the body, and at its front extremity passes through their internal organs, there will be found some points of simi- the nervous tract (as we have seen), and opens on the under side larity, but a great many points of difference.

of the body. The heart is situated above the food canal, and Both are elongated animals, and both can be divided by a just under the hard covering of the back. We have, therefore, mid-vertical section into two similar halves. The outer covering the main blood system situated above the food canal in the of the fish, though it is covered with small scales, is thin and contre, and the nervous system below it; these two latter, howflexible. It offers but little resistance to pressure, and no firm ever, crossing one another and exchanging places just at the support, or fixed point, from which muscles can play upon the front of the animal. All these structures are contained within limbs. It, moreover, manifests no tendency to division into seg- one tube, which is the hard covering of the animal. ments or rings. Turning to the lobster, we find it is enclosed Contrasted with this arrangement is that of the fish. In this in a hard, inflexible armour, which is divided into segments or animal the food canal occupies the same central position, but rings, placed one behind the other. This division is well marked the heart, instead of lying above it, lies on the under side. The and complete in the hinder part of the body, where there are nervous system does not consist of a series of knots, but of seven hard annular pieces united by softer membrane. They continuous column, and it is contained not in the tube which overlap one another above, but are separated below. The great lodges the other viscera, but in another tube, formed of bony shield which covers the head and fore part of the body also arches springing from the back-bone, and which is saper-imposed consists of fourteen segments, but they have all become united. on the other tube. The relative arrangement is best understood This thick, hard outer covering is the only solid part of the by a reference to the illustration, where transverse sections animal, and therefore to this must be attached the muscles at are given, supposed to be taken from the parts of the animals both ends ; that is, both at the fixed point of support from which where the lines marked a b cross the lateral views of the they pall, and also at the part of the body or limbs which they lobster and haddock. are intended to move. This arrangement is carried out even to The fish and the lobster, then, present two types of structure the limbs, whose joints are likewise cased in separate hard which are utterly different in many fundamental points, and if

in the comparison we have seized on those points which are of unsymmetrically throngh the body, their number and position greatest importance, we shall find that when we compare any being very various in the different divisions of the sub-kingdom. other animals belonging to these branches, first to the one type Organs of secretion, nutrition, and propagation more perfect than and then to the other, in reference to these peculiarities, we shall those of locomotion and animal life. have no difficulty in classifying them either in one division or Molluscoida.--Animals having tho general character of the the other.

Mollusca, but distinguished from them by having hearts of a A dog, for instance, though a very different animal from a simple saccular character without division, or noite at all. With fish, is like it in the points we have noted. It has a back-bone ciliated tentacles disposed in a circle or horse-shoe shape round of jointed vertebræ, and a columnar nervous system. It has the mouth. no segmented external skeleton. It has but four limbs, and its Annulosa (from annulus, a ring).--Animals with a body com. jaws are not paired limbs lying side by side, but are placed one posed of a longitudinal series of more or less distinctly developed above the other. A dragon-fly is very different from a lobster ring-like segments, which are more or less repetitions of one in less fundamental particulars, but in the essentials named it is another, according to the lower or higher position of the species. like to it. It has a chain of double nerve masses on the floor of The horny or leathery exteriors of these rings form an exoits tubular body, crossed by the food canal between the first and skeleton, to which the muscles are attached, and which forms a second messes; and so we might run on through the whole of protective envelope to the body. Nervous system consisting the structure, and show that it was really built upon tho same of a double chain of ganglia. Every organ or system of organs general plan as the lobster.

bi-laterally symmetrical. Locomotive organs and organs of The sub-kingdom to which the fish belongs is called Vertebrata, sense attain in this class a high development. a vertebra being the technical name given to one of the joints Annuloida.- Animals somewhat like the Annulosa, but the of the back-bone. This name vertebra was given because the perfect form is developed within a ciliated larva. fact that the back-bono was so sub-divided enabled its elements Coelenterata.-Animals whose alimentary canal freely comto turn one on another (verto being the Latin for to turn). municates with their body cavity. Body consisting of two

The lobster belongs to the invertebrate animals, but the foundation membranes of definite cellular structure. invertebrates include more than one sub-kingdom, and that to Protozoa.-Animals whose body consists of a sarcode subs: which the lobster belongs was called by Cuvier Articulata, stance, which has no definite cellular structure, but which is because they are jointed as to external skeleton of both body elastic, extensile, and albuminous in composition. They have no and limbs. Articulus is the Latin for a joint.

nervous system or organs of sense, but have structures called If, instead of a dog or a dragon-fly, we had taken a slug, we respectively nucleus and contractile vesicle. should have found that while the arrangement of the nervous, If the student finds these descriptions hard to understand, he blood, vascular, and food systems to one another was quite must wait for explanation till the following lessons are before different from the fish, and similar to the lobster, yet we should him. It is now necessary to be concise, even at the risk of being have found no hard jointed body, no chain of double ganglions obscure. on the floor of the body, and no limbs. This animal, therefore, belongs to neither of these types, though it is, of course, an invertebrate.

LESSONS IN LATIN.--XVI. The student is now prepared for the enumeration of the sub- RELATIVE AND INTERROGATIVE PRONOUNS. kingdoms and their characters. They are these :

Relative-Qui, quæ, quod, who or which. Interrogative-Quis, Vertebrata,

quæ, quid ? who or which ? S

Annulosa - Articulata of
).

Annuloida, Cuvier.
Colenterata.

Singular.
Protozoa,

Cases.
It should be noted that the form in which these are given has N.

qui, who;
quæ, who;

quod, which. a meaning. That the Vertebrata stand at the top of the scale is

G. cujus, whose ; cujus, whose; cujus, of which. admitted by all ; the Protozoa are as unquestionably the lowest

D. cui, to whom ; cui, to whom; cui, to which animals, and next above them come the Celenterata. It is, how. Ab. quo, by whom ;

Ac. quem, whom; quam, whom; quod, which, ever, impossible to determine whether the Mollusca or the Arti

qui, by whom;

quo, by which, alata are the higher animals. The Mollusca seem, in the

Plural. higher members of their branch, to approach most nearly to the N. qui, who;

quæ, who;

quæ, which. vertebrates, but the higher members of the branch Articulata G.

quorum, whose;
quarum, whose;

quorum, of whicha, are of such beautiful and complicated structure that they cer

D. quibus, to whom; quibus, to whom; quibus, to which. tainly cannot be placed lower than the Mollusca. We are com

Ac.
quos, whom;
quas, whom;

quæ, which. pelled, therefore, to range them side by side, at a like elevation.

Ab. quibus, by whom ; quibus, by whom. quibus, by which, We proceed to give the characters of the sub-kingdoms :1. Vertebrata.--Animals, the main trunk of whose nervous sys

Singular. tem consists of ganglionio matter massed together in the form of N. quis ?

quis ? before a noun, quid ? before a pons, a column. It is found on the dorsal (upper) aspect of the body,

quod ? its axis lying in the median vertical plane which divides the G.

cujus?
cujus ?

cujns ? animal into two symmetrical halves. This main nervous trunk D.

cui ?
cui ?

cui? consists anteriorly of the brain and posteriorly of the spinal Ac.

quem ?
quam ?

quid cord. It is usually enclosed in a bony or cartilaginous cavity

Ab. quo ? formed by the upper arches of the vertebra. The bodies of

Plural. these vertebræ form the essential portion of an internal bony or N.

quæ ?

quæ ? cartilaginous (gristly) skeleton. The column thus formed is G. quorum ?

quarum ?

quorum? placed immediately below the central nervous trunk, and sends D. quibus ?

quibus ?

quibus ? upward processes to form a series of dorsal arches to defend the Ac. quos ? nervous axis, and downward a series of less perfect arches, in

Ab. quibus ?

quibus ?

quibus? which lie the circulatory and alimentary organs. Appended to The preposition cum is sometimes set after the pronoun; as, this column, which forms the axis of support and resistance quocum, quacum, quibuscum, with whom, with which. whereon the rest of the skeleton hinges, are (normally) four Quis is repeated so as to form the compound prononn quislimbs, two anterior and two posterior. The blood is red, and quis, whosoever. In this case, both parts are declined thus: enclosed in vessels. Jaws playing vertically.

quisquis, m.; quæquæ, f.; quicquid, n. When the neuter is Mollusca (from mollis, soft). - Animals with soft bodies enveloped used as a substantive it is generally written quidquid. Take in soft skin, which is constantly moist, which is itself muscular, as instances : quoquo modo res habet, in whatever way the thing and to it the museles are attached. This skin has usually the is; quicquid id est, whatever that is. In quicunque, whosoever, power of secreting within or upon its tissues a calcareous extra- the qui is declined, and to its parts cunque is added, as cujus. vascular secretion (the shell). The nervous masses are dispersed / cunque, quodcunque, etc.

RELATIVE.

M.

F.

INTERROGATIVE.

quw?

qua?

quo ?

qui ?

quas ?

que ?

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