LARGEST RIVER If! THE WORLD Natural History of the Amazon. Piscatorial Wonders of the Stream Prof. Agassiz's Lecture on the Fiehes of the Amazon. Their Species, Habits, Characteristics, and Commercial Value. Etc., Ktc, Ktc., Etc., Ktc., Ktc. jLJuu'i-rmru u'u ji.r.nnnnriiiii"i" " " " " " Trot. Agassi, the great American naturalist and savan, Laving recently returned from a journey of scientific exploration in South Ame rica, is now engaged in making his discoveries known to the world in a series of lectures at the Cooper Institute, in New York city. We have already given sketches of several previous lectures, and we now reproduce a verbatim report of the most interesting address, that upon the " Fishes of the Amazon" a sub ject fraught with vital import in the scientilic world, and, as eliminated by Agassiz, is full of that popularity and simplicity that charm the million. STATEMENT OF THE SUBJECT. Ladies and Gentlemen: The aquatic popu lation of any extensive fresh water basin has many points of interest; We may, in the first place, view it in reference to the structure of these animals, as compared with that of aerial and terrestrial beings. We may examine them with reference to their geographical distribu tion as contrasted with those which inhabit the pea or the land. We may also examine them with reference to their variety, or the diversity which exists among them, under apparently identical circumstances. This last point is one cf peculiar interest; because you v, ill perceive that, if externaljcircunistances have had a deep influence in bringing about die variety of living beings which we find everywhere on the surface of the earth, we should expect to find great similarity among animals living close together, under identical circumstances, Fhut out from the inlluences of the great changes which are constantly taking place in the atmosphere, shut out from the great diversity of the bottoms which are found along the sea-shores, and circumscribed ' within limits very similar. Now, the Amazon, above all the rivers of the earth, presents a variety of organized beings which is stupendous, which exceeds all conception, and which was a matter of surprise even to me, who had de voted my life chiefly to the study of fishes. I will, therefore, try to give you some idea of this diversity. I regret only that I cannot sud denly impart to you the interest which I have felt for a long time in these animals. Unknown and uninteresting in their ways, they have generally been neglected. Few naturalists have turned their attention to them, and I am afraid you will find my lecture rather mono tonous. Yet, if you will for a moment consider that a knowledge of these beings has an im portant bearing on some of tho most important questions which are now under discussion among naturalists, I hope you will follow mo in the details which 1 am about to submit to you. riSCATOIUAL STRUCTURE. But first allow mo to say a few words con cerning the structure of aquatic animals. In the infancy of our science, animals were classi fied, that is, were brought together in groups, according to the conditions under which they are found in nature. If you will turn over the works of the great naturalists of the eleventh century, you will find 'that their descriptions of the animals then known are arranged under 1) nt few heads, one embracing the aquatic ani mals, another the terrestrial or creeping ani mals, and the other the aerial or flying animals, lint in proportion as our information of the structure of all these beings has been growing, it has been found that these external influences do not so modify organized beings as to bring together in the same habitation those which have the closest resemblance; and we are no longer surprised now to find in the water ani mals of the most diversified classes, or to find the same diversity among those which either inhabit the laud or live in the air. It lias been the result of modern investigation to discover that ' animals, however numerous, however varied, are, alter all, built upon four plans of structure only. Those plans are very simple, and may be recognized easily; and these sys tems may bo expressed by formulas so simple that you will permit me for a moment to call your attention to that point. curious formations. There are animals which have all parts ar ranged like rays around a central axis that is, they are radiated in structure ; and a figure like this (draws a star-shaped character on" t lie blackboard) may be considered as a formula expressing those peculiarities of structure, fchipposo that "we consider any organ, the sto mach for instance ; it will be found to have live pouches radiating in five different directions. Suppose that we consider the nervous system it will be found to consist of live ring's, live nwellings, with tho same directions as the live pouches of the stomach ; live rays or threads having the same direction, and "may be at the ends of the threads there may be eyes. The ovaries will be arranged in the same manner, with a bunch of eggs here, a bunch of eggs here, a bunch of eggs here, and another there. And all those parts are so arranged around a central axis, that they are like spokes of a wheel rays around a vertical axis ; and in that axis we have the mouth at the centre. So these animals, owing to this peculiarity of con stitution, are justly called Radiates. Now, of those we do not find any in the Amazon. We do not find any in the fresh waters except one, the simplest kind of polyp, the fresh water polyp, or bush polyp, as it is called; this is the only fresh water specimen of that large family which is innumerable in salt water, such as the jelly-fishes, star-fishes, and sea-urchins in fact, most of the animals that inhabit tho nea, and which have existed not only at all times during geological periods anterior to ours, but which are now common everywhere in the ocean, but which have no representa tive on land, and but a few very simple ones in the fresh waters of the temperate xono. Another group, which are called luolhisks, embrace animals the body of which is sym metrical, the parts of which are arranged around two sides of a longitudinal axis, so that these animals have an anterior and a posterior part a part that is above and a part that is lielow a right and a left, which is not the case with the radiates; for these radiates may move iii the direction of either of these 7I1E DAILY EV&NlKG Tl LEG IU IB. I IilLADELPHIA, THURSDAY, rays they have no right 'and no left; for if you call Mm the front, this may be right and thin left;' but' if yon call thin front, thi is right and this left, so that you have to introduce an arbitrary distinction, when you hoar described these radiate animals, with reference to which is the right and which tho left side, which is the part that is above, and which is the part that is below. PECULIARITIES OF TUB MOI.LUBKH. Not so with the mollusks. They havo in ternal features, which determine their relations, their symmetry, and fix the position of their parts in a manner which enables us to distin guish the anterior or head end from tho pos terior or tail end, as well as the right and left, and above and below. To this group of animals belong all the shell-fishes the clams, oysters, ahd the like, the snail and the cuttle-fishes also. 1'art of them are aquatic animals that inhabit the sea, part of them are fresh water fishes, and part of them are terrestrial animals. So you see, here we have animals of one and the same structure inhabiting tho different elements, which were made in the infancy of our science, the foundation of the classification of the whole animal kingdom. Of this typo there are several classes three classes and to them 1 shall refer presently, as we have a number of representatives of them in the fresh water animals of the Amazon. Let me say that the majority of those which have two valve are either fresh water or marine, the. greater part, however, marine, and the less are fresh water. Of those which have only one valve, anil are generally wound up in a spiral, we have also a majority in the sea, but some in fresh water, and some on land. Of the cuttle fish class there are none in fresh water, none are terrestrial, but all of them are marine. And they have been inhabitants of our globe from the very earliest periods of the earth's history during .which animals have lived upon it. I may represent the formula of these animals in this way (illustrating on the blackboard), the anterior end marked by some prominent feature which indicates something of a head. Not all, however, have the anterior end very different from the posterior. A longitudinal axis, on the side of which organs are arranged. For instance, in tho oyster there is a pair of pills on each side, so that the respiratory organs are placed on the right and on the left; while about the sides of the mouth are those fiat appendages, with the aid of which these animals introduce food into their mouths, and the organs, the intestines, the ovaries, the heart, .and the organs of respiration are clus tered in the centre. Now, the manner in which these several parts are protected by shell are accessory details of their structure, which cause the different families, different generas, and different species. THE ARTICULATES. Then we have another group which are called articulates, animals the body of which may be compared to a cylinder, or to a tube, but a tube divided into a number of rings, movable one upon the other, so that, in fact, the body is an articulated cylinder containing a single cavity, in which are arranged all the organs. 1 represent that in this way (makes a drawing); these transverse rings in this man ner; the internal organs arranged in the inte rior; the alimentary canal in the interior; the respiratory organs in the upper part; the ner vous system mainly in the lower part; tho respiratory organs upon the sides; and on the rings are frequently locomotive appendages in the shape of limbs, which may be mere hoops, as in the case of the worms, or may be articu lated limbs, as in the ease of crabs, lobsters, insects, and the like. Now, these articulated animals embrace also several classes of such worms, of which there are marine kinds, and fresh water kinds, and terrestrial kinds. It is one of the class which has tho most extraordi nary distribution, for worms are found every where. They are found even as parasites in the bodies of other animals; in the internal organs of other living beings; they are found in fresh water and salt water, and also in tho earth, burrowing under tho ground. IDENTITY OF STRUCTURE. Then we have the class of crabs, tho crus taceans, which is next above, and that of in sects which contain animals breathing air and living out of the water. So that we have here again, animals of an aquatic, or terrestrial, or aerial mode of life, all showing one and tho same structure. I like to insist upon these facts, which are most brilliant results of modern progress or science, because you see at once what bearing they have upon the question of the origin of these things. If we have identical structures under the most di versified conditions of existence, these external things which act upon living beings cannot have been the cause which has produced such unity of plan. The unity of plan that ideal common basis of animals must be derived from something higher than the conditions in which these animals live, when we find that, notwithstanding these diversified conditions, the animals present one and the same plan and structure. (Applause.) The next tyie is that of vertebrata. It is one which has a special interest for us, for we belong there (laugh ter), and with us all the animals which have a backbone, all the animals which have an in ternal solid axis so arranged as to surround two distinct cavities in which the various organs of the body are inclosed, one cavity below that axis in which all these parts or all those systems of the organs are contained by which life is maintained in its normal condi tion. These are the organs of digestion through which food is assimilated and trans formed for the sustenance of the body, the organs of breathing in which this assimilation is fostered, the organs of circulation through which the result of these operations is circu lated through the system, and also the organs if reproduction. All these organs by which animal life is simply maintained are con tained in the lower cavity of the body, while an upper cavity contains organs which establish the relations between the animals and the surrounding world. In that upper cavity is contained, in the anterior part of the body, the brain, and in the middle and posterior part's of the body the prolongation of tho brain which we call "the spinal marrow. From it arise the nerves, which are scattered through all parts of the body, and send sensibility and also receive impressions from the outside. To this centre is attached the organs of the senses, and which communicate directly with the cen tral mass of the nervous system. All these patts are contained in the upper cavity of tho body, and the whole is surrounded by llesh and inclosed in a skin, ami whatever bo the typo of vertebra which we take for examina tion, whether man or quadruped, bird, reptile, snake, turtle, or fi..h, all have the same identi cal structure, and these structures differ only in the form and complication of the execution, but in no way dues the plan differ in the slightest degree. A shark or a perch, a man or a bird, have the same identical plan of structure, and we could make a cut across their body, through the neck, the head, the chest, or the tail, and compare one with the other, and we would find that the. sections had tho same organs which had tho same relations to one another; and if wo compared one section in the same body with the other, a cut made through the head, or through tho middle, or 1 through the hind part of the part ng;uji, we would find the same relations, so wonderful is the idea which is manifested in this innumerable variety. And now let mo show you that this is not a fanciful assump tion. (The Professor here drew the form of ft fish on tho blackboard). We havo here the hacklione, here the upper spine of the skele ton, here also the ribs, here the head, tho mouth, the base of tho organs of tho senses, the eyes, the nostrils, and bo on. Suppose we make ft section across the body here through the centre of the body, or here through the head, or here through the tail, thero will be a difference in form no doubt, there will be a difference in he relative dimensions of tho parts, but there will be no difference in the relative position of these parts, and in the na ture of these parts. Suppose I commence with the section across the middle of the body. The first thing we find in the centre is the solid axis, above that we have these spires, which are in reality an arch covering a cavity; wo have here below the ribs, which are another arch inclosing another cavity; this is the lower cavity, which contains, as I have said, the organs of digestion, the intestines, liver, and the like. In the anterior part of tho body wo should lind the heart, in the middle region we should find the large vessels which run parallel to the hacklione, in the upper cavity we fchould find the spinal marrow, ajid on the outside of that tho masses of flesh which are covered by the skin. And now in the tail wo should have exactly the same thing, only that the central backbone is surmounted by a smaller arch. The intestines do not extend here except in the form of vessels and nerves, and here we have a prolongation of the spinal marrow, and we have flesh around here as before. Now, in the head is the difference. This upper portion is largely developed, iu comparison w ith the lower portion. This upper portion becomes the skull. Inside is the extensive mass of the brain. This is the base of the skull. Instead of ribs we have the lower jaw attached. Upon the sides of the skull we.have masses of flesh, which keep in motion these parts which are on the side, and tluv whole is surrounded by skin, as here. So that the whole difference is that the cavity of the intestines is reduced to a cavity of the mouth opening outside, just as the alimentary canal is a continuation of the cavity of the month and the spinal marrow of the brain. The brain is only an enlarged portion of the spinal marrow, or, to reverse it, the spinal marrow is a modification of the brain extend ing through the body. So that you see that my assertion is true, that in what ever region we may make a section to examine the relative positions of the organs of the vertebrata we find the organs identical, bearing the same relation to one another. If time would permit I could readily show you that whatever the form of an animal, whether it be a fish or a serpent, whether a lizard or a a turtle, or a bird, the relation of the parts is again the same, and the differences are chiefly differences in Torm and development. And it is in consequence of this great similarity that the idea has been started that all these animals may be derived one from the other; that all these animals may be the result of successive modifications of the few. You see on the one hand we have these uniform conditions which sustain the most diversified forms; then again w e have this unity of plan, which seems to bo in contradiction to the variety of inlluences under which these animals exist. DIVERSITY OF FORM. Then again we have an extraordinary diver sity of forms, which seem to indicate the most diversified organs; and yet such is tho similarity among these various things that they seem to be only a modification one of the other. No wonder, therefore, that investiga tors should make it their special object to study these things, and that they should differ in their opinions so much that there should be those who cannot conceive the cause of this diversity, unless it be the immediate manifes tation of a special creative act on the part of a Heing capable of producing at once perfect beings; while others, more inclined, perhaps, to follow development and progress than to look at first causes of all things, would rather have everything derived from a few primary forms which have undergone extraordinary changes in the course of time. To this subject I shall return in my last lecture. I can only point at present to tho liearing which these in vestigations of structural relations have upon the question of origin, upon the question of diversity, and upon the question of Unity in diversity. EVIDENCES OF ONE SUPREME CREATOR. For all things that exist in some jKiint of view are alike, chiefly by the unity which pre vails throughout nature; while from another point of view everything seems different; and when we come to consider what may be the origin of all things, we are at once led, on the one hand, to tho evidences of the workings of one mind, and, on tho other hand, to the ever changing conditions under which everything lives; and in consequence of that these various opinions some assuming that all things have grow n out of the change of a few things, and others assuming that everything must have been made as it is by a Supreme l'ower. (Ap plause.) THE ANIMALS OF THE AMAZON. Now, with these facts before us, we can turn our attention to the animals of the Amazon, and I may say that they comprise two different types of the same animal. We find in the Amazon, in these fresh waters, mollusks, and they belong to two classes. We find in the Amazon articulates, and they belong to two classes. We find worms and "crustacea. Wo find vertebrates in the Amazon, and the v belong to more than one class. Wo have fishes and we have also reptiles, and among them some that are aquatic while others are terrestrial; we have birds, some of which are aquatic ami others aerial and terrestrial, and we have mam malia or quadrupeds, some of which are aquatic. And not the least of the singular features of this immense basin of fresh water is the presence in it of several representatives of the porpoise family. Tlie great family of w hales, to which the porpoise belongs, has live representatives in the Ama.on in tho form of a variety of porpoises, and of that other singu lar animal which the Brazilians call the beshuyUiy, nnd which we have translated into sea-cow, about which I shall have something more to say hereafter. Then let us remember tliis, that in one and the same stream, exhibiting this unity of tem perature ol which I have treated in' a former lecture, we have animals of different types of structure mollusks, articulates, and verte biates, while no radiates have ever been found in it; and m these three types we have repre sentatives ol several classes. Now let mu sav w hat classes they are, so that I may impart a more definite idea upon that point. Classes in the animal kingdom have long been circum scribed by naturalists to suit their fanev, or according to heir impressions. It seems de sirable to determine the classes according to some principle; and the principle w hich ap pears the most natural as the basis of limita tion ot the c asses, in the various modes of execution of these plans of structure. After show ing you that vertebrates havo one common- plan of structure, we will divide that type into classes according to the maimer in which the plan is carried out. If the back bone is constructed in the fashion of fishes, if it consists of spines of backbone which aro united together by double conical cavities; if the flesh is white, and arranged in large masses on the sides of the backbone; if the organs of respiration are gills instead of lungs; if the organs of inhalation exhibit a heart Which has only a single sack from which the blood is pro pelled to all parts of tho body, and another sack to rc ceive the blood which comes from all parts of the liody, instead of the complicated circulation which we find in birds and in mam malia, w e say that we have here one mode of execution of the plan of structure, which justi fies us in considering fishes as a natural class. If, on the contrary, we have animals which have warm blood, which breathe through the lungs, which have a double circulation, the body of w hich, instead of lieing covered with scales, is covered with feathers, if these ani mals, in bringing forth their young, lay eggs upon which they sit, producing young which they rear, we have indications of another mode of execution of that plan of vertebrates; and we consider ourselves justified in calling birds a class in the animal kingdom, and so on. Now, among mollusks, we have three classes, one of which is particularly characterized by tho manner in which the parts are arranged on the tw o sides of the body, in broad flappers, or biofid curtains hanging on the sides of the axis, and generally protected by hard shells that aie double, that is, one on each side; and that class embraces all the so-called bivalve shells. Of this class, the Amazon contains a considerable variety, and so do all our fresh waters, our rivers and lakes. VARIETY OF MOLLUSKS. Iii tho ocean there are numerous forms, but no one of these bivalve shells living upon tho land or in tho atmosphere, or that can sustain itself outside of water. Then we have another class among these mollusks which embrace all those the body of which has respi ratory organs only on one side of the body namely, the body of which is more or less twisted, frequently coiled up in a spiral, and in which tho anterior end of tho body is pro vided with appendages looking something like horns tentacles frequently, at the end of which are eyes, like our snails. They consti tute a second class. Of this class of snails we find quite a variety in the fresh water in the Amazon, and in still greater variety upon land, living upon trees and decaying wood, or upon the soil, burrowing in the earth during the dry season. So that of the three classed of mollusks which exist all over the world, we havo representatives of two in the fresh water of the Amazon, and of one of those two we find also representatives on land. There is a curious feature among these fresh-water bivalve shells to which 1 wilt hero allude their strange resemblance to marine shells, notw ithstanding the difference of their internal structure. THE AMERICAN BIVALVES. You all know how numerous fresh-water muscles are in our waters, and how great is the diversity of tho fresh-water shells in the estern waters. 1 he Ohio and its tributaries, the Tennessee and the Cumberland rivers, and the rivers that empty into the Uulf of Mexico, and all the Southern rivers, teem with a variety of bivalve shells, all of which have the same internal structure, consisting of this (il lustrating by drawing the parts as described); that the middle axis may be protruded in the shape of a ileshy foot, with which the animals creep on the ground or in the wood. At tho sides aro two flappers, which surround the mouth, to aid in introducing food into the alimentary cavity. Then, there are two gills hanging right ami left. Inside here is a sack which contains the organs; and here is a large fleshy mass which extends acrosstho body, and' here another; so that upon a transverse section of these animals we would see one valve turning this way and tho other that way. And here is one of those bundles extending from one valve to another, so as to bring them together; and here is another. Now these fresh water shells .of ours vary in external appearance greatly. Some are smooth and have a thin shell, and have an oviate form. Others are elongated in this way; others are more triangular; others have tubercles on their surface; others havo spines projecting from the surface; others have lows of ribs thus, and others rows of ribs in this manner. But while the different species thus differ in their external appearance, their internal structure is everywhere ifie same. PECULIARITIES. The species- of the Amazon havo another curious feature that they are not only iden tical in structure with our own, and identical among themselves in structure, but their ex ternal forms are the marine shells, which have a totally different structure. Those among you who know tho shell of the razor-fish, called the razor-shell (a very slender and straight shell of this form), will bo surprised to hear that there aro fresh-water shells of that form in tho Amazon, which, far from having anything in their internal structure which resembles the solens (as this is called by naturalists), have all the internal structure of our common fresh water muscles. There are, others which have the external appearance of tho mother-of-pearl bivalve shell, exhibiting the external appear ance of that group. A third variety exhibits the peculiarities of our area, having transverse waves alternating with furrows, such as are only known in the family of the marine area, and yet found in some of these fresh-water shells. What does that mean 1 It is dillicult to say why there should bo, as it were, a reminiscence of the sea among animals of the fresh waters, superimposed upon a structure which has no similarity to the structure of these marine shells. MYSTERIES OF THE ClftATlVK POWER. 1 can only see in this the working of mind, which combines elements diversified among themselves, and hardly any indication of the transformation of one type into the other. Hut, without expressing a decided opinion about it, let me tell you that those are tho huts upon which naturalists agree, and in consequence of which they present such various opinions, such .conflict ing views. Tho naturalist who recognizes only this similarity between the shells of the Amazon and the marine shells, w ill at once jump at the con clusion that the Amazon Valley was once under the sea, and that when it rose some species remained in . the pools that wero left, and when those basins were changed into fresh water in the course of time, these marine shells changed to what they aro now. But he who.rememU'rs that these fresh-water shells have none of the internal structure of (he niaiine shells w hich they resemble in external appearance, will say: '-But if these external ciicunistances have so modified the marine shells, what has given them a common char acter in which they agree so closely with one another .'" For not only do they not differ iu internal structure in any way among them selves but they resemble the fresh-water shells'found elsewhere ill this world, as in North America or in Kurope. Thero must Ihj some other cause at work, not only to pro duce the change, but thero must' be some cause to impart unity notwithstanding the cl,ugC a unity which extends not to the Aiiuuou only, but to nil other part of tho FEBRUARY 21, 1867. world. The fact is Unit the world is more mysteiious than our philosophy has fathomed thus far, or tlian man can yet compass m ui narrow systems. (Applause.) THE KISIIKS rKOPKR. Tn the Infnncv of our science, all the inhabit ants of the fresh water were railed fishes, and it is only in projHirtioii as we have lieeomo acquainted with these structural differences, that this class of fishes, embracing so much, thus varied in structure and plan, has iteen gradually referred to different classes. I will now pass on to tho fishes proper, to those re presentatives of the fiesh watvr which instruo ture resemble man, and which share with us that plan of structure which is common to the birds and reptiles and quadrupeds, as well as to man and the fishes proper. If the time per mits I shall close with a few remarks upon the fresh water inhabitants of the typo ot tho ver tebrates, worms, and crustacea; but if not, I shall defer my remarks upon those classes to my next lecture. 1 feel somewhat emoarrassca to speak of fishes without saying something of the fundamental differences which exist among them; and that I may better bring before you the differences which characterize the dif ferent groups of fishes, let me draw the outlines of some of them, and point out to you the permanent differences which distinguish them. Suppose I take, first, our trout. You perceive here that the head and body run together so that there is hardly a distinct neck. That is a characteristic feature of all fishes. It is only in the class of reptiles that we begin to perceive the first indication of the contraction between the head and body which indicates the position of the neck. What is characteristic of this type of fishes, is the position of the fin upon the back, which is called the dorsal. There is a large fin at the vnd of the tail, which may be cut square, as in the fresh-water trout; which may be forked as in the sea-trout; or which may have its upper end prolonged greatly, as in'some other representatives of the family. This is the caudal, and that fin is the organ with which these fishes impart to themselves an onward motion. POSITION AND USES OF TIIE FINS. Striking right and left with the tail, the body is propelled forward in consequence of this motion, and this motion is aided by the dorsal. This other I'm under the tail is called the anal. When the fish strikes violently and raises that fin, the surface with which he strikes the water is enlarged; but when he strikes gently, this fin is bent under the tail, and the surface with which he strikes the water is diminished, and the force with wliich he strikes being slight,' the motion is comparatively feeble. The fin is the ventral. This is on the medial line of the bod v. There is one above, the dorsal, and one below, tho anal, and the cau dal at the end of tho body. The caudal in this group of fishes is always semicircular; that is, the upper half corresponds with the lower half. If the tail is cut square, then the two parts are alout the same; and if it is forked, then the upper part is of about the same dimensions as the lower. It is rarely the case that one of those parts is slightly longer than the other, and it may be either the upper or the lower. For instance, in the llying-fish, which comes very near this, we have the lower lobe (somewhat longer than the upper. With this, the moment the fish emerges from the water, it gives its last impulse by striking violently to the right and left several times in rapid succession. We have, also, upon each side of the body one on the right and one on the left; those fins which are near the head, which are, in fact, upon the sides of the chest, and which are known by tho name of tho pectorals; and these which are here, upon the lower sides of the abdominal cavity, are known as the ab dominal fins. In all the fishes of this group we have the abdominal fin, half way between the pectoral and tho anal fins. Now let us compare w ith that ,a perch, a common yellow perch, as we hae them in our fresh water. Here (drawing) we have a very different dor sal; there are two, commonly large. We have the caudal comparatively small and feeble. We have the anal placed in about tho same position as in the trout, but it has a strong spine in front 'of tho fin. Then wo have the pectorals placed here, and the ventrals, in stead of occupying a medial position, are placed just below the pectorals, and the front part of tho ventrals sustains a strong spine. You see at once what a difference that makes. This first tin consists of strong spines, while the second fin consists of a number of rays which are divided and subdivided so that the whole fin is soft and tender, while this is very hard and prickly. So are the spines here ; so are tho spines there ; and on the sides of the head there aro other spines connected with the liones of tho head. But that is not all. Let us examine the mouth, llere the mouth is very widely cleft, perhaps, but there are also perches in which the mouth is very widely cleft. THE JAWS AND TEETH. But the principal difference is that here, in the front, the interior of the upper jaw is made up of one bone, and the posterior part of "the upper jaw of anoher bone, which two bones are placed one in succession to the other, forming one arch, and Loth have teeth along their lower edge. These two bones are exactly the same as those w hich form the upper margin of our own mouth. The anterior part of the mouth is occupied by the cutting teeth; then follow the eye teeth, then the grinders. Now , there are two cutting teeth, on the right and the left side, which are implanted in a bono w Inch corresponds to this, and is called the intermaxillary. The eye-teeth and grinders are implanted in another bone, which is called tho upper maxillary, and tho intermaxillary anil upper maxillary together, in one arch, form the margin of the mouth. Now in the perch it is very different. We have one bone w liich extends in this way from the anterior part of the mouth to the end of the cleft, and that one bone is provided with teeth along its margin, and forms alone the upper margin of the mouth; w hile another .bone, placed be hind, and foiming in no way a part of the mouth, sustaining no teeth wlmtev..i- r..,.. sents the upper maxillary. It is the anterior bono which repiesents the intermaxillary, so that the proper jaw-bone in the perch has not a tooth. It does not form a part of the ante rior margin of the mouth, while the inter maxillary is so large that it alone forms the arch ol tho upper part of tho mouth. These are the most prominent differences that we have here. THE SHARK AND STt'UliEO.N. . And now there aro fishes of a Very different typo hem these (draws the outline of a fish on the blackboard). I suppose you may recog nize hero a Shark. (Applause.) It differs tiein the two typos of fishes I have doserilod t bus iar in having five clefts upon tho bides of the head, which are the gill openings. The trout has only one, and so has the perch only one, and that cleft is supported by a bony plate which moves to and fro upon the gills and protects them during respiration. And so has the lu rch, while tho shark has no such bono, and the branchial fissures are oin in advance of the large fin, wliich is placed upon the side, and the ventral nas agaiu the same position as m the trout or salmon, while the tail is re- rrmrkablo for the prolongation of its upper lobe; and that is not only an external pro longation, but the backlKtne itself ex tends into this lolo to its very end. So that its hacklione dies not terminate as in other fish, with a broad blade supporting tho tail, or as in the front, salmon and the like, but tho hacklione extends to the very end. All these fishes, moreover, have tfleir solid frame, that is their skeletons, soft and consisting more of cartilage tlu.n bone. (Makes a drawing of tho sturgeon on the blackboard.) It differs from the shark, in having the gills protected, like the other fishes, by a bony plate, and so that the gills are covered externally. In having the snout so prolonged, the mouth is far below the head. And then it shares with the shark that singu lar prolongation in the tail which I have noticed. And it has that very singular fea ture, that tho ventral fins occupy the middle of the abdominal region, half way liefrween tho ' pectorals and the anals. And, finally, thero is this last type f fish (makes a drawing of it), which is quite curious for its elongated form; for the truncated termination of the head, wliich is, as it were, cut square; and for the presence of the Bimple fin extending all over the body, without any pectorals or ventrals, but with a number of small openings upon tho side, as many as seven, and one upon the back. It is called the lamper-eel. To these groups belong all the fishes known on the earth; and to these groups may be referred all the fishes that have lived in all times. (Ap plause.) But then they assume such extra ordinary differences in details that, by a pro cess of changing some part or other, we can at once see how one might have grown out of the other; or wo can see that by a difference of execution the same idea may have been ex pressed in different ways. And here I at one express the different views which are enter tained concerning these affinities. They niiy be the manifestations of the same idea ex pressed in different ways, or they may be modi fications of a few primitive facts. TUE AMAZON 11 AS FISHES OF ITS OWN. Now, what are the fishes which inhabit the Amazon 1 for I wanted to say all this as pre paration to give you some definite idea of the various types of fishes which we find in that mighty basin. Not one of those fishes with wliich we are familiar in our rivers is to be found there. Not one of those which are in all of the rivers of Kurope is to be found there. Not one from any other fresh-water basin is to be found there. The Amazon has fishes of its own, entirely different from those of any other basin. And these fishes are different even from those of other fresh-water rivers of Brazil. And in each part of the Amazon there are fishes of a peculiar character; so that those which in habit the lower course, of the Amazon, say below the mouth of the Tocautins, as far as the contact of the salt with fresh water, differ from those which are found in the river lietweenthe Tocautins and tho Xingu. At the month of the Xingu, we have fishes differing from those w hich inhabit the Tapajos. As we ascend from tho Tapajos and enter the district of the Kio Madeira, we find still other fishes. If we go into the district of the Rio Negro, we find still iifferent ones; and if we go further up on the orders of other livers which I have explored there are peculiar fishes. TWO HUNDRED VARIETIES OP FISU IN ONE SMALL LAKE. And so great is tho variety that in 6inall lakes of water we find endless varieties, while in Manias, at the junction of tho Kio Negro with the Amazon, I was led to examine one particular little lake of a very few hundred square yards in extent, with the view of ascer taining how great that diversity among fishes may bo which occupy a circumscribed area, and in that pool for it is hardly anything more; it is only a few hundred square yards at low water, and only a few thousand square yards at high water in that small lake I have found in the course of two months, during several excursions, over two hundred different kind of fishes (applause) three times as many as aro known from the Mississippi, three times as many as are known from the Nile, or Sene gal, or Ganges. And the number found in the w hole basin of tho Amazon is not less than two thousand different kinds that is, ten times as many as were known to Linmeus about a cen tury ago, from the whole world. (Applause.) And strange to say, it would appear that iu proportion as we became acquainted with a large number of these animals, they should be found to resemble one another more and more; but on the contrary, such are the peculiarities of their features, such is the principle of their differentiation w hich brings about the differ ences we notice among them, that pi propor tion as I found a larger and larger ' number, I found that tho difference between them seemed 0 grow. And you will understand that. It seems paradoxical, and yet it is strictly so. Concede for a moment that we have here extreme points (illustrating with dots on the board), be tween wliich there are certain intermediate foims: Now, suppose that this represents the varieties known w hen I went to the Amazon the sum total of the fishes described by my predecessors, including all the various expedi tions which had gone to that country with a view of studying its natural productions the total. number of fishes then known did not exceed one hundred and fifty, and the number 1 have brought home exceeds 1500 it ap proaches 201 Ht. (Applause.) And yet I say that now the difference which we know to exist between them is greater when we take any two than the difference which existed between them when we knew only 150. Every new one has exhibited radiations, modifica tions in the direction of almost every other, so that the points of contact have, as it were modified not only in point of resemblances, but in point of differences, in consequence of which the sum total of difference which is now known among these 2H00 fishes far exceeds the extreme differences which appeared when only the few hundreds were known before. (Ap plause.) THE SWORDFISH. And now I should like to give you some idea of w hat are those differences, and what is the appearance of some of these fishes, and of the mode in which they differ from the fishes of our own waters. In tho first place, the type of sharks lias only ine representative in the Amazon that is tho swordtish. The sword fish is a shark which differs from ordinary sharks in this, that the skull is prolonged here.. You will see how by a mollification of the lorn of some part we obtain widely different forms. Tho swordlish is a shark, the snout of w liich is prolonged to a considerable extent, on the twp sides of which project large teeth, forming tint saw characteristic ot that genus. Now the swordlish is the only kind of shark which is known to enter the large rivers. It is not pro perly an inhabitant of the river. It is found on tho seashore, and so is tho same species found at the ;nouth of tho Mississippi, and another species found at the mouth of the Senegal, on the other side of tho Atlantic. This is tho only representative of that group of fishes wliich wo have in the,Auuuon. The kimpor-eel type, of which we have quite a variety throughout our fresh-water streams, has not a single representative in the whole basin of the Amazon. It is entirely foreign to the tropical waters of the Ainiuou, but it fr
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