Part 66

Agassiz’s beautifully illustrated “Contributions to the Natural History of the United States” cover many subjects in morphology and embryology, which are treated with such thoroughness and breadth of view as to give them a place among the zoological classics. The Essay on Classification, the North American Testudinata, the Embryology of the turtle, and the Acalephs are the special topics. These are summarized and discussed at length in the Journal (=25=, 126, 202, 321, 342, 1858; =30=, 142, 1860; =31=, 295, 1861).

The volume on the “Journey in Brazil” (1868) in joint authorship with Mrs. Agassiz is a fascinating narrative of exploration.

The conceptions which Agassiz held as to the most essential aim of zoological study are well illustrated in his autobiographical sketch, where he writes:

“I did not then know how much more important it is to the naturalist to understand the structure of a few animals, than to command the whole field of scientific nomenclature. Since I have become a teacher, and have watched the progress of students, I have seen that they all begin in the same way; but how many have grown old in the pursuit, without ever rising to any higher conception of the study of nature, spending their life in the determination of species, and in extending scientific terminology!”

It is not surprising, then, that under such influence the older systematic studies should be replaced in large measure by those of a morphological and embryological nature.

The personal influence of Agassiz is still felt in the lives of even the younger zoologists of the present day. For the investigators of the present generation are for the most part indebted to one or another of Agassiz’s pupils for their guidance in zoological studies. These pupils include his son Alexander Agassiz, Allen, Brooks, Clarke, Fewkes, Goode, Hyatt, Jordan, Lyman, Morse, Packard, Scudder, Verrill, Wilder, and others—leaders in zoological work during the last third of the nineteenth century. Through such men as these the inspiration of Agassiz has been handed on in turn to their pupils and from them to the younger generation of zoologists.

The essential difference between the work of Agassiz and that of the American zoologists who preceded him was in his power of broad generalizations. To him the organism meant a living witness of some great natural law, in the interpretation of which zoology was engaged. The organism in its structure, in its development, in its habits furnished links in the chain of evidence which, when completed, would reveal the meaning of nature. Of all Agassiz’s pupils, probably William K. Brooks most fittingly perpetuated his master’s ideals.

Period of Morphology and Embryology, 1847–1870.

The new aspect of zoology which came as a result of the influence of Agassiz characterized the zoological work of the fifties and sixties, that is, until the significance of the natural selection theory of Darwin and Wallace became generally appreciated.

The work in these years and well into the seventies was largely influenced by the morphological, embryological and systematic studies of Louis Agassiz and his school. The structure, development, and homologies of animals as indicating their relationship and position in the scheme of classification was prominent in the work of this period. The adaptations of animals to their environment and the application of the biogenetic law to the various groups of animals were also favorite subjects of study.

The most successful investigators in this period on the different groups of animals include:—Louis Agassiz on the natural history and embryology of coelenterates and turtles; A. Agassiz, embryology of echinoderms and worms; H. J. Clark, embryology of turtles and systematic papers on sponges and coelenterates; E. Desor, echinoderms and embryology of worms; C. Girard, embryology, worms, and reptiles; J. Leidy, protozoa, coelenterates, worms, anatomy of mollusks; W. O. Ayres and T. Lyman, natural history of echinoderms; McCrady, development of acalephs; W. Stimpson, marine invertebrates; A. E. Verrill, coelenterates, echinoderms, worms; A. Hyatt, evolutionary theories, bryozoa and mollusks; Pourtales, deep sea fauna; C. B. Adams, A. and W. G. Binney, Brooks, Carpenter, Conrad, Dall, Jay, Lea, S. Smith, Tryon, mollusks; E. S. Morse, brachiopods, mollusks; J. D. Dana, coelenterates and Crustacea; Kirtland, Loew, Edwards, Hagen, Melsheimer, Packard, Riley, Scudder, Walsh, insects; Gill, Holbrook, Storer, fishes; Cope, evolutionary theories, fishes and amphibia; Baird, reptiles and birds; J. A. Allen, amphibia, reptiles and birds; Brewer, Cassin, Coues, Lawrence, birds; Audubon, Bachman, Baird, Cope, Wilder, mammals.

The progress of ornithology in the United States previous to 1876 is well described in a paper by J. A. Allen in the American Naturalist (=10=, 536, 1876). A sketch of the early history of conchology is given by A. W. Tryon in the Journal (=33=, 13, 1862).

Jeffries Wyman was the most prominent comparative anatomist of this period. His work includes classic papers on the anatomy and embryology of fishes, amphibia, and reptiles.

Zoology in the American Journal of Science, 1846–1870.

The fifty volumes of the second series of the Journal, including the years 1846 to 1870, cover approximately this period of morphology and embryology. During this period the Journal occupied a very important place in zoological circles, for J. D. Dana was for most of this period the editor-in-chief, while Louis Agassiz and Asa Gray were connected with it as associate editors. Moreover, in 1864 one of the most promising of Agassiz’s pupils, Addison E. Verrill, was called to Yale as professor of zoology and was made an associate editor in 1869.

In the Journal, therefore, may be found, in its original articles, together with its reports of meetings and addresses and its reviews of literature, a fairly complete account of the zoological activity of the period. The most important zoological researches, both in Europe and America, were reviewed in the bibliographic notices.

The most important series of zoological articles are by Dana himself. As his work on the zoophytes and crustacea of the U. S. Exploring Expedition continued, he published from time to time general summaries of his conclusions regarding the relationships of the various groups. Included among these papers are philosophical essays on general biological principles which must have had much influence on the biological studies of the time, and which form a basis for many of our present concepts.

The importance of these papers warrants the list being given in full. The titles are here in many cases abbreviated and the subjects consolidated.

General views on Classification, =1=, 286, 1846.

Zoophytes, =2=, 64, 187, 1846; =3=, 1, 160, 337, 1847.

Genus Astraea, =9=, 295, 1850.

Conspectus crustaceorum, =8=, 276, 424, 1849; =9=, 129, 1850; =11=, 268, 1851.

Genera of Gammaracea, =8=, 135, 1849; of Cyclopacea, =1=, 225, 1846.

Markings of Carapax of Crabs, =11=, 95, 1851.

Classification of Crustacea, =11=, 223, 425; =12=, 121, 238, 1851; =13=, 119; =14=, 297, 1852; =22=, 14, 1856.

Geographical distribution of Crustacea, =18=, 314, 1854; =19=, 6; =20=, 168, 349, 1855.

Alternation of Generations in Plants and Radiata, =10=, 341, 1850.

Parthenogenesis, =24=, 399, 1857.