The next year showed that his over-burdened life was beginning to tell upon his health. Scarcely had he arrived in Charleston and begun his course at the Medical College when he was attacked by a violent fever, and his life was in danger for many days. Fortunately for him his illness occurred at the "Hollow Tree," where he was passing the Christmas holidays. Dr. and Mrs. Holbrook were like a brother and sister to him, and nothing could exceed the kindness he received under their roof. One young friend who had been his pupil, and to whom he was much attached, Dr. St. Julian Ravenel, was constantly at his bedside. His care was invaluable, for he combined the qualities of physician and nurse. Under such watchful tending, Agassiz could hardly fail to mend if cure were humanly possible. The solicitude of these nearer friends seemed to be shared by the whole community, and his recovery gave general relief. He was able to resume his lectures toward the end of February. Spite of the languor of convalescence his elastic mind was at once ready for work, as may be seen by the following extract from one of his first letters. TO JAMES D. DANA. SULLIVAN'S ISLAND, CHARLESTON, February 16, 1853. . . .It seems, indeed, to me as if in the study of the geographical distribution of animals the present condition of the animal kingdom was too exclusively taken into consideration. Whenever it can be done, and I hope before long it may be done for all classes, it will be desirable to take into account the relations of the living to the fossil species. Since you are as fully satisfied as I am that the location of animals, with all their peculiarities, is not the result of physical influences, but lies within the plans and intentions of the Creator, it must be obvious that the successive introduction of all the diversity of forms which have existed from the first appearance of any given division of the animal kingdom up to the present creation, must have reference to the location of those now in existence. For instance, if it be true among mammalia that the highest types, such as quadrumana, are essentially tropical, may it not be that the prevailing distribution of the inferior pachyderms within the same geographical limits is owing to the circumstance that their type was introduced upon earth during a warmer period in the history of our globe, and that their present location is in accordance with that fact, rather than related to their degree of organization? The pentacrinites, the lowest of the echinoderms, have only one living representative in tropical America, where we find at the same time the highest and largest spatangi and holothuridae. Is this not quite a parallel case with the monkeys and pachyderms? for once crinoids were the only representatives of the class of echinoderms. May we not say the same of crocodiles when compared with the ancient gigantic saurians? or are the crocodiles, as an order, distinct from the