Louis Agassiz: His Life and Correspondence

by Louis Agassiz

(4.) Will you give me, in a few general words, your views of the scale occupied by the fish of the Old Red, considered as a natural group? Are they so rudimentary as to look like abortions or creatures derived from some inferior class, which have not yet by development reached the higher type of fish? Again, I should say, NO; but I long for an answer from a great authority like yours. I am most anxious for a good general conception of the fish of the Old Red, with reference to some intelligible scale.

(5.) Lastly, is there the shadow of ground for supposing that by any natural generative development the Ichthyosaurians and other kindred forms of reptile have come from Sauroid, or any other type of fish? I believe you will say, NO. At any rate, the facts of geology lend no support to such a view, for the nobler forms of Reptile appear in strata below those in which the Ichthyosaurians, etc., are first seen. But I must not trouble you with more questions. Professor Whewell is now Master of Trinity College. We shall all rejoice to see you.

Ever, my dear Professor, your most faithful and most grateful friend,

A. SEDGWICK.

FROM LOUIS AGASSIZ TO A. SEDGWICK.

NEUCHATEL, June, 1845.

. . .I reproach myself for not acknowledging at once your most interesting letter of April 10th. But you will easily understand that in the midst of the rush of work consequent upon my preparation for a journey of several years' duration I have not noticed the flight of time since I received it, until to-day, when the sight of the date fills me with confusion. And yet, for years, I have not received a letter which has given me greater pleasure or moved me more deeply. I have felt in it and have received from it that vigor of conviction which gives to all you say or write a virile energy, captivating alike to the listener or the reader. Like you, I am pained by the progress of certain tendencies in the domain of the natural sciences; it is not only the arid character of this philosophy of nature (and by this I mean, not NATURAL PHILOSOPHY, but the "Natur-philosophie" of the Germans and French) which alarms me. I dread quite as much the exaggeration of religious fanaticism, borrowing fragments from science, imperfectly or not at all understood, and then making use of them to prescribe to scientific men what they are allowed to see or to find in Nature. Between these two extremes it is difficult to follow a safe road. The reason is, perhaps, that the domain of facts has not yet received a sufficiently general recognition, while traditional beliefs still have too much influence upon the study of the sciences.

Wishing to review such ideas as I had formed upon these questions, I gave a public course this winter upon the plan of creation as shown in the development of the animal kingdom. I wish I could send it to you, for I think it might please you. Unhappily, I had no time to write it out, and have not even an outline of it. But I intend to work further upon this subject and make a book upon it one of these days. If I speak of it to-day it is because in this course I have treated all the questions upon which you ask my opinion. Let me answer them here after a somewhat aphoristic fashion.

I find it impossible to attribute the biological phenomena, which have been and still are going on upon the surface of our globe, to the simple action of physical forces. I believe they are due, in their entirety, as well as individually, to the direct intervention of a creative power, acting freely and in an autonomic way. . .I have tried to make this intentional plan in the organization of the animal kingdom evident, by showing that the differences between animals do not constitute a material chain, analogous to a series of physical phenomena, bound together by the same law, but present themselves rather as the phases of a thought, formulated according to a definite aim. I think we know enough of comparative anatomy to abandon forever the idea of the transformation of the organs of one type into those of another. The metamorphoses of certain animals, and especially of insects, so often cited in support of this idea, prove, by the fixity with which they repeat themselves in innumerable species, exactly the contrary. In the persistency of these metamorphoses, distinct for each species and known to repeat themselves annually in a hundred thousand species, and to have done so ever since the present order of things was established on the earth, have we not the most direct proof that the diversity of types is not due to external natural influences? I have followed this idea in all the types of the animal kingdom. I have also tried to show the direct intervention of a creative power in the geographical distribution of organized beings on the surface of the globe when the species are definitely circumscribed. As evidence of the fixity of generic types and the existence of a higher and free causal power, I have made use of a method which appears to me new as a process of reasoning. The series of reptiles, for instance, in the family of lizards, shows apodal forms, forms with rudimentary feet, then with a successively larger number of fingers until we reach, by seemingly insensible gradations, the genera Anguis, Ophisaurus, and Pseudopus, the Chamosauria, Chirotes, Bipes, Sepo, Scincus, and at last the true lizards. It would seem to any reasonable man that these types are the transformations of a single primitive type, so closely do the modifications approach each other; and yet I now reject any such supposition, and after having studied the facts most thoroughly, I find in them a direct proof of the creation of all these species. It must not be forgotten that the genus Anguis belongs to Europe, the Ophisaurus to North America, the Pseudopus to Dalmatia and the Caspian steppe, the Sepo to Italy, etc. Now, I ask how portions of the earth so absolutely distinct could have combined to form a continuous zoological series, now so strikingly distributed, and whether the idea of this development could have started from any other source than a creative purpose manifested in space? These same purposes, this same constancy in the employment of means toward a final end, may be read still more clearly in the study of the fossils of the different creations. The species of all the creations are materially and genealogically as distinct from each other as those of the different points on the surface of the globe. I have compared hundreds of species reputed identical in various successive deposits,—species which are always quoted in favor of a transition, however indirect, from one group of species to another, —and I have always found marked specific differences between them. In a few weeks I will send you a paper which I have just printed on this subject, where it seems to me this view is very satisfactorily proved. The idea of a procreation of new species by preceding ones is a gratuitous supposition opposed to all sound physiological notions. And yet it is true that, taken as a whole, there is a gradation in the organized beings of successive geological formations, and that the end and aim of this development is the appearance of man. But this serial connection of all successive creatures is not material; taken singly these groups of species show no relation through intermediate forms genetically derived one from the other. The connection between them becomes evident only when they are considered as a whole emanating from a creative power, the author of them all. To your special questions I may now very briefly reply.

Have fishes descended from a primitive type? So far am I from thinking this possible, that I do not believe there is a single specimen of fossil or living fish, whether marine or fresh-water, that has not been created with reference to a special intention and a definite aim, even though we may be able to detect but a portion of these numerous relations and of the essential purpose.