Louis Agassiz: His Life and Correspondence

by Louis Agassiz

[Probably 1852,—date not given.]

. . .What a time has passed since my last letter! Had you not been constantly in my thoughts, and your counsels always before me as my guide, I should reproach myself for my silence. I hope my two papers on the medusae, forwarded this year, have reached you, and also one upon the classification of insects, as based upon their development. I have devoted myself especially to the organization of the invertebrate animals, and to the facts bearing upon the perfecting of their classification. I have succeeded in tracing the same identity of structure between the three classes of radiates, and also between those of mollusks, as has already been recognized in the vertebrates, and partially in the articulates. It is truly a pleasure for me now to be able to demonstrate in my lectures the insensible gradations existing between polyps, medusae, and echinoderms, and to designate by the same name organs seemingly so different. Especially has the minute examination of the thickness of the test in echinoderms revealed to me unexpected relations between the sea-urchin and the medusa. No one suspects, I fancy, at this moment, that the solid envelope of the Scutellae and the Clypeasters is traversed by a net-work of radiating tubes, corresponding to those of the medusae, so well presented by Ehrenberg in Aurelia aurita. If the Berlin zoologists will take the trouble to file off the surface of the test of an Echinarachnius parma, they will find a circular canal as large and as continuous as that of the medusae. The aquiferous tubes specified above open into this canal. But the same thing may be found under various modifications in other genera of the family. Since I have succeeded in injecting colored liquid into the beroids, for instance, and keeping them alive with it circulating in their transparent mass, I am able to show the identity of their zones of locomotive fringes (combs), from which they take their name of Ctenophorae, with the ambulacral (locomotive) apparatus of the echinoderms. Furnished with these facts, it is not difficult to recognize true beroidal forms in the embryos of sea-urchins and star-fishes, published by Muller in his beautiful plates, and thus to trace the medusoid origin of the echinoderms, as the polypoid origin of the medusae has already been recognized. I do not here allude to their primitive origin, but simply to the general fact that among radiates the embryos of the higher classes represent, in miniature, types of the lower classes, as, for instance, those of the echinoderms resemble the medusae, those of the medusae the polyps. Having passed the greater part of last winter in Florida, where I was especially occupied in studying the coral reefs, I had the best opportunity in the world for prosecuting my embryological researches upon the stony corals. I detected relations among them which now enable me to determine the classification of these animals according to their mode of development with greater completeness than ever before, and even to assign a superior or inferior rank to their different types, agreeing with their geological succession, as I have already done for the fishes. I am on the road to the same results for the mollusks and the articulates, and can even now say in general terms, that the most ancient representatives of all the families belonging to these great groups, strikingly recall the first phases in the embryonic development of their successors in more recent formations, and even that the embryos of comparatively recent families recall families belonging to ancient epochs. You will find some allusion to these results in my Lectures on Embryology, given in my "Lake Superior," of which I have twice sent you a copy, that it might reach you the more surely; but these first impressions have assumed greater coherence now, and I constantly find myself recurring to my fossils for light upon the embryonic forms I am studying and vice versa, consulting my embryological drawings in order to decipher the fossils with greater certainty.

The proximity of the sea and the ease with which I can visit any part of the coast within a range of some twenty degrees give me inexhaustible resources for the whole year, which, as time goes on, I turn more and more to the best account. On the other hand, the abundance and admirable state of preservation of the fossils found in our ancient deposits, as well as the regular succession of the beds containing them, contribute admirable material for this kind of comparative study. . .

In the summer of 1851 Agassiz was invited to a professorship at the Medical College in Charleston, S.C. This was especially acceptable to him, because it substituted a regular course of instruction to students, for the disconnected lectures given to miscellaneous audiences, in various parts of the country, by which he was obliged to eke out his small salary and provide for his scientific expenses. While more fatiguing than class-room work, these scattered lectures had a less educational value, though, on the other hand, they awakened a very wide-spread interest in the study of nature. The strain of constant traveling for this purpose, the more harassing because so unfavorable to his habits of continuous work, had already told severely upon his health; and from this point of view also the new professorship was attractive, as promising a more quiet, though no less occupied, life. The lectures were to be given during the three winter months, thus occupying the interval between his autumn and spring courses at Cambridge.

He assumed his new duties at Charleston in December, 1851, and by the kindness of his friend Mrs. Rutledge, who offered him the use of her cottage for the purpose, he soon established a laboratory on Sullivan's Island, where the two or three assistants he had brought with him could work conveniently. The cottage stood within hearing of the wash of the waves, at the head of the long, hard sand beach which fringed the island shore for some three or four miles. There could hardly be a more favorable position for a naturalist, and there, in the midst of their specimens, Agassiz and his band of workers might constantly be found. His studies here were of the greater interest to him because they connected themselves with his previous researches, not only upon the fishes, but also upon the lower marine animals of the coast of New England and of the Florida reefs; so that he had now a basis for comparison of the fauna scattered along the whole Atlantic coast of the United States. The following letter gives some idea of his work at this time.

TO PROFESSOR JAMES D. DANA.

CHARLESTON, January 26, 1852.

MY DEAR FRIEND,

You should at least know that I think of you often on these shores. And how could I do otherwise when I daily find new small crustacea, which remind me of the important work you are now preparing on that subject.

Of course, of the larger ones there is nothing to be found after Professor Gibbes has gone over the ground, but among the lower orders there are a great many in store for a microscopic observer. I have only to regret that I cannot apply myself more steadily. I find my nervous system so over-excited that any continuous exertion makes me feverish. So I go about as much as the weather allows, and gather materials for better times.