First in his father's counting house, and then at a boy's school near Niagara, young Brooks bravely gained the means to pursue higher branches of natural history, and to devote himself to research. In the former position he realized how futile for him would be a life given to money-getting, and he palliated the uncongenial nature of that life by such abstract thought as seemed useful, one immediate result of which was the invention of a mechanical device for computing interest and discounts in sterling money, that had considerable circulation. This, though it scarcely indicated a stronger bias for mathematics than for Nature study, showed a latent possibility that was not to be developed. In the latter position, which brought him in close contact with the wonders of time action, so plainly read in one of Nature's books for the blind—Niagara Falls—he found food for thought, as well as a deep interest in the action of young minds. Here was much material for philosophical study of wood life too, as well as for growth of conceptions of the way to learn and to teach.
Free, after serving three years, to follow his genius, Agassiz's romantic venture at Pennikese drew this young naturalist, as it did so many of that epoch; and henceforth marine life, with its revelation of fundamental problems, fascinated him. Working on at Agassiz's museum, learning its collections by heart, absorbing from this center of American natural history and from its founder both stimulus and method, influenced deeply also by the unobtrusive teachings of McCrady and others who helped to make Cambridge the Mecca of naturalists, he was already an active contributor to the discussion of problems in the embryology of animals when he won his Ph. D. degree in 1875.
Quiet, diffident, slow to speak, leaving hasty action, too, for those of other constitution, with thoughtful brow and keen eye to look outward, as well as to regard inner thought, this young man with flowing beard was a noticeable person. At this time he was to be seen always accompanied by his faithful "Tige"; for, wiser than Ulysses, he shared all the hardships and joys of life with this loved companion.
Now he sought his true environment, and found it in the new university starting in 1876—the Johns Hopkins University. There he was appointed Fellow, an honor subsequently won by many who are well known to biological science, as W. T. Sedgwick, E. B. Wilson, K. Mitsukuri, A. F. W. Schimper, H. H. Donaldson, H. L. Osborn, J. McKeen Cattell, H. H. Howell, A. T. Bruce, E. S. Lee, H. E. Nachtrieb, W. Noyes, J. Jastrow, E. B. Mall, H. V. Wilson, C. E. Hodge, S. Watase, and T. H. Morgan. Like C. O. Whitman, in 1879, he did not enter upon the privileges of that position, but as instructor and associate became at once a guiding element in the new growth. In the freedom from old traditions, from fixed conventions and routines offered by this new university, this peculiar original mind found its best environment, and while the opportunity doubtless did much for the man, the man certainly reacted most favorably for the welfare of the highest ideals of his new home.
We find him at once outspoken in emphasis of the philosophical aspect of animal morphology, contributing thoughts upon "inductive reasoning in morphological problems," upon "the relation between embryology and phylogeny," upon "the causes of serial and bilateral symmetry," and upon the "rhythmic nature" of the cleavage of an egg. Yet this period was also, and pre-eminently, one of acquisition of hard-earned and detailed facts. The development of Pulmonates and Lamellibranchs, of Crustacea and of Medusæ, as well as of the marvels of Salpa's life history, became absorbing studies.
This great field of the morphology of nonvertebrates could be properly worked only with access to the marine fauna, and at that date there were few facilities for seaside study in America. A true disciple of Louis Agassiz, Professor Brooks saw the need of a marine laboratory, and devoted himself, as Dohrn did at Naples, to the accomplishment of an end so necessary for the advance of natural science. Encouraged by the aid of a few citizens of Baltimore, in 1878 there was started an experiment—"The Chesapeake Zoölogical Laboratory," at Fort Wool, Va., with Professor Brooks as director. With the absolute devotion of its director to research as example, and with the liberal aid of the trustees of the Johns Hopkins University, this laboratory became a most important adjunct to the university and a virile center of zoölogical study. So great was its success as a factor in the advance of zoölogical knowledge that the trustees bravely continued to support it whenever financial disaster did not rob them of the last penny. For eight years in the Chesapeake, or in the remoter waters of North Carolina, the station flourished; then, in 1886, we find the director, with a few enthusiastic students, venturing in a small schooner to the but little known Bahama Island, Green Turtle Cay, there to enlarge their experiences with such delightful realization of naturalists' dreams of the tropics as Haeckel experienced in his Journey to Ceylon. Subsequent annual expeditions to Nassau, the Bemini Islands, and to various parts of Jamaica served as marked eras in the lives of many young naturalists who will not soon forget the contact with life thus obtained.
From these sources and from his connection with the United States Fish Commission, as director of the Marine Station at Woods Holl, Mass., in 1888, Professor Brooks drew inspiration and fact for the work and thought by which he is so well known to the working naturalist. There are few great divisions of the animal kingdom that have not excited his special interest and claimed his long-sustained labor upon the problems they express. Like McCrady, deeply fascinated by the Hydromedusæ and their wonderful changes, many smaller papers, as well as the Memoir of the Boston Society of Natural History, entitled The Life History of the Hydromedusæ and the Origin of Alternation of Generations, testify to his success in unraveling plots that thickened with new discoveries.
An early interest in the mollusca, shown by his doctor's dissertation upon the embryology of the fresh-water mussels, printed in part in the Proceedings of the American Association, 1875, continued to be expressed in his contributions to many problems in the embryology of the fresh-water Pulmonates, of Gasteropods, of Lamellibranchs, and of the Squid. The Crustacea also rightly claimed a large share of the attention of a philosophic naturalist, bringing him face to face with the rigid formulations of law which these creatures present. The discovery of the very exceptional method of cleavage in the egg of the decapod Lucifer, and the demonstration of the existence of a free Nauplius stage there (published in the Philosophical Transactions of the Royal Society in 1882), marked a most important advance in the morphological interpretation of all Crustacea, and brought its author to the first rank as an authority upon this much-studied group. Studying and capturing at Beaufort those phantom-like sand burrowers, the Squilla, gained him an insight into and an interest in this strange division of Crustacea that enabled him to undertake that difficult task, the description of Stomatopods collected by the Challenger Expedition—a task completed in 1886. The report, published in such a magnificent series as only the British Government could have consummated, is noticeable for the author's clear, free illustration of the creatures described and classified. In it we find a classification of the numerous, weird, glassy larvæ, agreeing with the classification of the adults and marking the success of the solution of the problem—the reference of chance collections of various stages of many species to their proper places in the life history of each species.
When the fever for ancestral trees had spread among naturalists in a much more virulent form than that endemic in Wales, and when the Ascidians were brought into line as ancestral vertebrates, it was no wonder to find Professor Brooks laboring upon these interesting creatures, but his work in this group started from a different point of view. As early as 1875, when studying in the laboratory of Alexander Agassiz, he contributed to the Boston Society of Natural History a description involving a most novel interpretation of the embryology of a remarkable Ascidian, Salpa. This form is known to many not naturalists as that beautiful animal chain which is sometimes so common in the clear waters of Newport Harbor as to be dipped up in every bucket of water, but more often not there at all. The female buds forth male branches and gives each an egg (which is fertilized to form a second generation of females). There is thus no alteration of sexual and non-sexual generations at all; and, with characteristic appreciation of a paradox, Professor Brooks subsequently emphasized the fact that the poet naturalist Chamisso, in discovering, in 1814, "Alternation of Generations" in Salpa, had discovered a phenomenon where it did not exist, though subsequently found common enough in many other animals. With the continuity of interest so marked in him, the life history of Salpa, as thus revealed, continued to be one of the living thoughts in Professor Brooks's mind for a long period of years, and, with the accumulation of material and results of researches afforded by his summer work, culminated in the monograph Salpa—a quarto of nearly four hundred pages and fifty odd plates—published in 1893, or after nearly twenty years of sustained interest in this complex problem. In this volume we find first a coherent view of the intricate life history of this animal illuminated by such metaphors as make the necessary technicalities both readable and thinkable. For instance, "A chain of Salpa may be compared to two chains of cars on two parallel tracks, placed so that the middle of each car on one track is opposite the ends of two cars of the other track, and each joined by two couplings to the car in front of it on its own track, and in the same way to the one behind it, and also to those diagonally in front of it and behind it on the other track." Again, in speaking of that startling process of egg development that makes the embryology of Salpa one of the apparently insoluble problems of this branch of inquiry, he says: "Stated in a word, the most remarkable peculiarity of the Salpa embryology is this: It is blocked out in follicular cells, which form layers and undergo foldings and other changes which result in an outline or model of all the general features in the organization of the embryo. While these processes are going on the development of the blastomeres is retarded, so that they are carried into their final position in the embryo while still in a rudimentary condition. Finally, when they reach the places they are to occupy, they undergo rapid multiplication and growth and build up the tissues of the body, while the scaffolding of follicle cells is torn down and used up as food for the true embryonic cells. An imaginary illustration may help to make the subject clear. Suppose that while carpenters are building a house of wood the brick-makers pile clay on the boards as they are carried past, and shape the lumps of clay into bricks as they find them scattered through the building where they have been carried with the boards. Now, as the house of wood approaches completion, imagine the bricklayers build a brick house over the wooden framework and not from the bottom upward, but here and there wherever the bricks are to be found, and that as fast as parts of the brick house are finished the wooden one is torn down. To make the analogy complete we must imagine that all the structure which is removed is assimilated by the bricks, and is thus turned into the substance of new bricks to carry on the construction."
Following that descriptive portion of the work comes a most interesting interweaving of facts gathered in wide experience with a scientific imagination possible only to one who had lived and thought in close sympathetic contact with tropical marine life. It is an account of the present conditions of life along tropical shores and the probable steps that led to the evolution of the innumerable sedentary and creeping things from the ancestral forms that floated on the surface of the ocean before there were shores. Charming reading for the layman, and for the specialist a broadening poetic insight into life as it is and as it was when the world was young and the pelagic forbears of the vertebrates competed with their simpler associates in the annexation of the bottom as a vantage ground for the "benevolent assimilation" of later immigrants. The third portion of the work follows a most commendable plan: "Scientific controversy is so unprofitable that I shall try to make it as subordinate as possible, that the reader may devote all his attention to the life history of Salpa, without interruption at every point where my own observations confirm or contradict the statements of others." This section deals with the refutation of criticism of the author's interpretations, and endeavors to harmonize the discords that in this, as in all complex morphological research, make progress slow though surer.