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“ Thou cold-blooded slave,

Hast thou not spoke like thunder on my side ?
Beene sworne my soldier,
And dost thou now fall over to my foes?"-SHAKSPERE.

toads enabled to live embedded in rock

1034. Why are or stone ?

Because their skins are capable of effecting the necessary changes in the system when the function of the lungs is altogether arrested; and, requiring an inconceivably small portion of air, they are enabled to live by the supply which penetrates the pores of the material in which they are embedded.

MISCELLANEOUS.

1035. Why have most reptiles a kind of moveable lid at the aperture of their nasal organs ?

Reptiles are thus provided, so that when they are under water, the organ of smell may be exercised or protected as circumstances may require. The proper vehicle of the impression of smell in reptiles is air ; and this they draw through their nasal cavities during inspiration, effecting the operation by depressing their lingual bone, and thus enlarging the cavity of the mouth.

1036. Why can reptiles abstain for an extraordinary length of time from food and drink?

Because the languid circulation of their blood, their rare secretions, low temperature, and scaly and impermeable envelope, render their losses by evaporation from the skin very inconsiderable ; so that the frequent supplies which are wanted in other animals, to compensate for the incessant waste, are not required for reptiles.

1037. Why are reptiles termed cold-blooded ?

Because they do not produce enough heat to have a temperature sensibly higher than that of the surrounding air.

The whole of their body is heated or cooled at the same time as

“ Forthwith the sounds and seas, each creek and bay,

With frie innumerable swarme, and shoales
Of fish, that with their finnes and shining scales
Glide under the greene wave."-MILTON.

the surrounding medium ; and the changes of temperature which they thus experience have great influence upon all their functions.

A warmth of from 105° to 120° is soon fatal to most of these animals ; and cold tends to depress all their natural operations. In winter, most of them could no longer digest the food introduced into their stomach, and do not take nourishment. Their respiration also diminishes in a most remarkable manner. Thus, during the cold season, the action of the air on the skin is sufficient for the maintenance of the life of the frog; and the lungs of one of these animals may be removed without producing asphyxia ; whilst in summer they have need not only of the pulmonary respiration, but also of their cutaneous ; and death soon occurs when the air does not act on the skin, or is excluded from

the lungs.

CLASSIFICATION OF THE VARIOUS FISHES.

CLASS IV. -PISCES.

ORDER 1.-LEPTOCARDIA.*

1038. Why is the first order of fishes called leptocardia ?

From two Greek words signifying small and heart, with reference to the rudimentary formation of the heart, which, indeed, is said to be absent, and to consist entirely of the contractile power of the arteries.

1039. This order includes only a single small fish, which rarely attains a length of two inches, and which presents so many remarkable characters that its position in classification has been much disputed. This is the Amphioxus lanceolatus, a little, slender, transparent creature, found on sandy coasts in various parts of the world. Its body is of the lamprey form, with a narrow membranous border. The vertebral column is represented by a gelatinous cord, which supports the axis of the nervous system; the latter terminates anteriorly by a rounded extremity, without any signs of a brain. The head bears a pair of eyes, which are connected with the end of the nervous axis by short filaments, and there is an apparent

• The classification here pursued combines the systems of Cuvier and Agassiz, as blended by Müller.

“ Lie there, Lycaon : let the fish surround

Thy bloated corpse, and suck thy gory wound.”—PopE.

rudiment of an olfactory organ. The mouth is at the front of the head, where it forms an oval opening without jaws, but surrounded by a number of cartilaginous points; the oval cavity leads into a large branchial sac. By the action of cilia, with which these cavities are lined, currents are produced in water, the water passing off through numerous slits in its walls into the general cavity of the body, whence it escapes by an opening in the ventral surface.*

ORDER II.-CYCLOSTOMATA.

1010. Why is the second order of fishes called cyclostomata ?

From two Greek words meaning a circle and a mouth, in reference to the circular mouth which distinguishes the members of the order.

1041. They are of an elongated, cylindric, and worm-like form; the skin is tough and destitute of scales; the pectoral and ventral fins are wanting; the skeleton is cartilaginous; breathing orifices, little sacs that open exteriorly by separate vents ; heart muscular, composed of two chambers.

1042. Why has the lamprey a circular, cartilaginous mouth ?

upon the

Because it lives by suction, some species living upon insects and

worms: others
juices of the larger fishes.
One species, the hag, con-
trives to enter the mouths
of fishes, and extracts their
substance by sucking. Fish
that have been hooked on

lines, and allowed to remain in the water for some time afterwards, have been attacked by these creatures, and when drawn up have been found to consist of little more than empty skin.

[graphic]

It was

1043. Formerly the lamprey was 'a fish of considerable importance. taken in great quantities in the Thames, and sold to the Dutch as bait for turbot, cod, and other fisheries. Four hundred thousand have been sold in one season for

• Orr's “Circle of the Sciences.”

“ Let riches never breede a lofty minde,

Let nature's giftes make no man ouer blinde,
For these are all but bladders full of winde."-TURBERVILLE.

this purpose, at the rate of forty shillings a thousand. From five pounds to eight pounds a thousand has been given; but a comparative scarcity of late

years, and consequent increase in price, have obliged the line fishermen to adopt other substances for bait.*

ORDER III.-TELEOSTIA.

1044. Why is the third order of fishes named teleostia ?

From two Greek words signifying perfect, and bones, in reference to the perfect bony skeletons which they possess.

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The ORDER is again divided into six Sub-orders: 1. Physotomata ; 2. Anacanthina ; 3. Pharyngognatha; 4. Acanthoptera ; 5. Lopobranchia ; 6. Plectognatha

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1046. Why is the sub-order physotomata so named ?

From the Greek phuaso, to blow, or inflate, in allusion to the possession of an air-bladder, connected with the pharynx by a duct, which only occurs in these fishes, of all the teleostia.

1047. The fishes belonging to this group are usually furnished with a complete series of fins, which are always composed entirely of soft rays, with the exception

Yarrell's “ History of British Fishes."

Genius, piercing as the electric flame,

When waked in one, in others wakes the same."-SCOTT.

of the first ray in the dorsal, anal, and pectoral fins, which are sometimes spinous. The ventral fins are sometimes wanting ; when present, they are always abdominal in position. The skin is sometimes naked, at other times more or less covered with bony plates; in most cases, however, it is thickly clad with scales. The air bladder is connected with the pharynx by a sort of duct. The sub-order includes most of the important fishes that are sought for as food by man, and one species which possesses electrical powers.

1048. Why has the gymnotus the power of communicating electric shocks ?

For the purpose of defending itself from enemies, and also to benumb its prey, which is generally swifter in motion than the eel, until the latter can overtake it.

1049. That these are the reasons why this animal is endowed with this wonderful power there can be no doubt, since the uses made of the electric force by the eel have been well ascertained.

The electric eel is not only one of the most extraordinary of fishes, but it is one of the most wonderful productions of living nature. And yet it is no' more wonderful than the serpent which fascinates it prey; than the bird which baits with insects the branches of shrubs, in order to attract small birds thither ; than the fish which emits jets of water to knock down flies; or the spider which constructs a beautiful snare, and waits silently and motionless the entrapment of its victim.

These various means to the same end, with which different animals are endowed, illustrate the boundless resources of the Creative Wisdom.

The apparatus in which the electric power is lodged is a very singular one, consisting of four organs, which are placed longitudinally in the tail of the fish. The organic part of this singular apparatus consists of a countless assemblage of cells, which have some analogy to the divisions of a galvanic battery.

The nature of the shock transmitted appears to be galvanic or electrical. Nearly the same substances are conductors and non-conductors of the shock, as are conductors and non-conductors of common electricity. The eel may with perfect impunity be touched with a glass rod, or the hand wrapped in a dry silk handkerchief ; but metals, water, and almost all moist bodies conduct it readily. If the animal is touched with one hand only, that is, if it is touched only in one place, no shock is felt; but if it is touched in two places considerably apart from each other, the shock is very violent

The manner in which the force is applied is as follows :—The gymnotus approaches as nearly as possible its intended prey; the latter endeavour to escape, when the gymnotus discharges its battery, which has been found to be powerfully effective at a distance of fifteen feet. The creature thus benumbed is incapable of any further effort, and the eel swims leisurely towards and devours it.

The degree of force which can be thus exerted is considerable. Horses entering

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