Imatges de pàgina
PDF
EPUB

stronger than in those whose blood is warm. Their heart pulsates, in some cases, for many hours after it has been removed from the body; the tortoise will continue to live, and exhibit voluntary motion, for a considerable time after having lost its head. The physiologist Lewes affirms that a frog moved about voluntarily the day after he had removed its brain; and one was kept alive forty days after having been subjected to the total deprivation of its lungs. As might be expected from the character of their blood, its slow circulation, and the smallness of the brain, reptiles are in general sluggish and indolent in their habits of life, and obtuse9 in their sensations; and in cold countries they pass a great part of the winter in a dormant1o state. Almost all reptiles are carnivorous. They produce their young from eggs, which they generally deposit in warm sandy places, leaving them to be hatched by the warmth of the atmosphere.

6. Reptiles have been divided, by most naturalists, into the following four orders or classes: first, the Chelonians, or tortoises; second, the Saurians, or lizards, which embrace the crocodiles; third, the Ophidians, or serpents; and fourth, the Amphibians, which embrace the frogs, toads, salamanders, and sirens-animals which undergo a wonderful transformation12 at a certain period of their lives, from the nature and habits of fishes to those of the true land reptiles. Think not that the study of the nature, character, and habits of such creatures is unworthy the human intellect: they form links in the great chain of animated nature; and the great whole of this most interesting portion of God's creation can not be understood without a knowledge of the parts of which it is composed. We may well apply to this subject Pope's celebrated lines

"From Nature's chain, whatever link you strike,
Tenth or ten thousandth, breaks the chain alike."

VER'-TE-BRATE, an animal having a spine]
with joints.

2 AP-PAR'-ENT, easily seen; obvious.

3 TEM'-PER-A-TURE, state of a body with regard to heat or cold.

4 IN-VES'-TI-GATE, examine into.

5 STRUCT'-URE, form, make, construction.

6 AM-PHIB'-I-ANS, see page 72.

7 AU'-RI-CLE, one of the cavities of the heart

8

which receives the blood from the lungs of veins. See Fourth Reader, p. 49.

VEN'-TRI-CLE, a cavity of the heart which propels the blood to the lungs or arteries. See Fourth Reader, p. 49.

9 OB-TUSE', dull; not having acute sensi
bility.

10 DOR-MANT, sleeping; not active.
11 ۀR-NIV'-O-ROUs, feeding on flesh.
12 TRANS-FORM-A'TION, change of form,

LESSON II.-A LETTER ABOUT THE CHELONIANS.1

"What do you think of turtles' ?" Such was the question asked me by a young friend and former pupil of mine, then on a visit with me to our great metropolis,2 as, stepping out of a dining-saloon in Broadway, we stopped a moment to look at three enormous living sea-turtles that had just been deposited on the sidewalk from a dray-cart, with their backs downward to prevent them from running away. After some comments upon turtle-soup and aldermanic dinners, my young friend remarked that he knew very little about the better portion of the turtle family, and had a prejudice against the whole race: he had seen, he said, great numbers of ugly-looking mud-turtles in swamps and river-marshes, and he thought these reptiles were very well adapted, by their disagreeable appearance, to the places which they inhabit. With a promise to give my friend some account, by letter, of the turtle portion of the reptile kingdom, we parted; and now I proceed to make good my promise.

Dellwild, May 15th, 18-.

1. MY YOUNG FRIEND,-I begin this letter by recalling to your remembrance the substance of the remark which you made at our parting, "that turtles are peculiarly adapted to certain unpleasant localities which Nature seems to have set apart for them." A fit starting-place is this; for here, by your own admission, is a beautiful harmony3 in nature, which would not be if the loveliest of singing-birds inhabited the marshes, and turtles, lizards, and crocodiles crawled in our gardens. The same kind of harmony will be found to exist throughout earth, air, and water: the eagle and the condor naturally betake themselves to mountain heights far from the dwellings of man; gaudy sun-birds and delicate hummingbirds

"gleam between

The crimson blossoms of the coral-tree
In the warm isles of India's sunny sea;"

the lion for the forests, the tiger for the jungles, the fishes for the waters, and why not reptiles to crawl upon the earth, and turtles to wallow in the marshes? You may lay it down as a principle to begin with, that the harmony3 of nature would be incomplete if every nook of creation were not filled with its appropriate inhabitants.

2. But perhaps it may serve to give these lowly creatures

a greater degree of importance in your estimation, and dignify the study of their character and habits, to learn (if you are ignorant of it) that the celebrated naturalist Agassiz has devoted the greater part of one of his folio volumes upon the Natural History of the Animals of this Country to the subject of tortoises alone, and that he has filled the greater part of another volume with exquisite" drawings of these animals. Do you think it was time wasted on his part? or that the cause of science will not be benefited by his labors? Not content with information at second-hand, he has examined hundreds, and probably thousands, of the living animals themselves, and from his own personal knowledge has written his descriptions and made his drawings.

3. " Surely," you say, "he must have traveled much, and waded through swamps and marshes innumerable, to have found so many of these disgusting animals!" By no means. Breaking in upon the natural harmony to which we have alluded, he had his garden full of them, in the city of Cambridge, near Boston; and there he walked among them daily, fed them, and studied their character and habits. "But," you ask, "how did he obtain them'?" Scientific men from all parts of our country collected them for him, and sent them to him. Thus Agassiz tells us that a gentleman of Natchez, Mississippi, not satisfied with collecting, extensively, the turtles in the neighborhood of his residence, undertook a journey of many hundred miles for the special purpose of securing all the species living in the adjoining regions, and, having completed the survey, set out with a cargo of living turtles, and brought them safely alive to him in Cambridge, after a journey of over a thousand miles.

4. I think you will agree with me that if such a man as Agassiz, whose name is every where honored for his contributions to science, devotes so much time to the study of tortoises, and publishes costly books to explain their structure and describe their habits, it is surely not unworthy a student's ambition to learn something about these animals, and the position which they occupy in the kingdom of animated nature. You will doubtless admit that it is very desirable, to say the least, in an age when natural history is receiving so much attention, to have some general knowledge of all its great divisions, that of herpetology among the rest, that you may not be wholly ignorant of what the learned are so much interested in.

5. Let me remind you of another advantage which will be

the natural result of a more extended acquaintance with this subject. The feelings of disgust with which, doubtless, the sight of most reptiles now fills you, will give way to some degree of satisfaction at least, if not of pleasure, by reason of the interest which a knowledge of their structure, character, and habits will excite in you. If we could look upon all God's creatures with pleasure, and find something to interest us in all of them, even the humblest, how much would our stock of general happiness be increased thereby!

6. But let us return to our subject, and see if we can not treat of it in a more scientific order. As tortoises are included in the great division of vertebrated animals, you will naturally ask, "for what réason' ?" I reply, "Because they have a back-bone or spinal column." "But the tortoise," you say, "is a soft animal, between two shells, and I see no such bone in its body." Let me explain to you. The back-bone of the tortoise is on the outside of the body, and forms a part of its shell, or covering. Here is a drawing which will make it all plain to you. It represents the under side of the upper shell of the tortoise, with the bones of the limbs attached in their proper places. Downward through the length of the shell runs the spinal column; branching out from each side of it are the flat ribs, which have so grown together as to leave only a mere line-mark to show where they are united. Thus the spinal column and the ribs grow on the outside, so as to form the upper shell of the animal.

[graphic]

Upper shell of Tortoise.

7. "This is wonderful," you say; "what I had never thought of before." Do you see any wisdom', or apparent design', in such an arrangement'? The tortoise, when on land, is a slow animal, and it has a soft body, which, if unprotected, would be easily crushed, or destroyed by other animals. The peculiar growth of its back-bone and ribs has given it a firm bony shell to protect it from above; and in a similar manner the breast-bone, or sternum (which has been removed in the drawing), spreads out, in a shell-like form, extending from the base of the neck to the tail. By this singular provision the turtle is incased in a coat of bony armor, formed of its own skeleton! It will be well for you to recollect that the upper shell is called the carapace, and the lower one the plastron..

8

8. The Chelonian order of reptiles (for it is well to know the terms which scientific men use)-the Chelonians, I say, may be conveniently divided into the three following families: land tortoises, river and marsh tortoises, and marine turtles; although Agassiz divides them into two classes, with seven families in one, and two in the other, placing the land tortoises and the river and marsh tortoises in one class, and the marine turtles in the other. I shall not have room in this letter to describe any of these classes or families, but in my next I will give you some account of a few of the most important or most noted species.

1 CHE-LO'-NI-AN, from the Greek chel-o-ne, as
tortoise.

2 ME-TRUP'-O-LIS, chief city (New York).
3 HAR-MO-NY, just adaptation of parts to
each other.
[tory.
4 NAT'-U-RAL-IST, onc versed in natural his-8

6

AG-AS-SIZ (ig'-a-se, or a-gus'-siz).
FO'-LI-O, a book formed by once doubling
each sheet of paper.

Ex'-QUI-SITE, choice; exceedingly beauti-
ful.
CAR-A-PACE'.

LESSON III.-A SECOND LETTER ABOUT TURTLES.

[graphic][subsumed][subsumed][subsumed][merged small]

LAND, MARSIT, AND RIVER TORTOISES.-1. Salt-water Terrapin, Emys palustris. 2. Blanding's Tortoise, Cistuda Blandingii. 3. Spotted Tortoise, I'mys guttala. 4. Freshwater, or Wood Terrapin, Emys insculpta. 5. Alligator Tortoise, or Snapping Turtle, Emysaura serpentina. 6. Common Mud-Turtle, or Musk Tortoise, Sternotherus odoratus. 7. Matamata Tortoise, Chelys matamata. 8. Common Box-Tortoise, Cistuda Carolina. (Nos. 2 and 8 are Land Tortoises.)

Dellwild, May 24th, 18-. now to fulfill the prom

1. MY YOUNG FRIEND,-I proceed ise which I made in my last letter. Among the land tor

« AnteriorContinua »