former stream-planation and burial by mountain wash which by stream-action at a later stage is again removed the fact remains that the finest and most extensive rock-floors are found in situations where no water-action could possibly have occurred. For all these cases other suggestions of genesis is, of course, necessary. The local exhuming of the rock-floors of arid piedmonts by the removal of its wash mantle does not really demand any elaborate inductive reasoning in order to reach an adequate explanation of the phenomenon. It is one of the commonest features of the desert. The effect is sometimes repeated over the same district several times in a year. It has been known to take place over night-by wind action. In the semi-arid belt, or on the margin of lofty mountains, as the Sierra Nevada in California for example, the local removal of the soil layer might be at first glance ascribed to stream-action; but broader observation extending to typical desert regions, where only low hills prevail, demonstrates at once that the stream-planing hypothesis must be entirely abandoned. The extension of moist-climate principles of erosion to arid lands is done with constantly growing difficulty. In support of the idea of the eolic derivation of many rock-floored piedmont plains there are ample published observations. The late W J McGee's descriptions of the phenomenon as displayed in Sonoran deserts are pertinent. A single experience of my own when encamped on the Jornada del Muerto at the northern end of the Mexican tableland is by no means an isolated instance. There at the foot of a mountain apparently "buried up to its shoulders in its own débris " a strong gale which suddenly arose completely swept away in a half hour's time the supposedly deep soil and laid bare the smoothest and hardest of rock-floors worn out on the upturned edges of most resistant strata. Since the situation was at the mouth of a canyon and upon the back of what appeared to be a broad alluvial fan, a day's later visit might have ascribed the phenomenon to streain work. CHARLES KEYES NOTES CONCERNING THE FOOD SUPPLY IN the literature dealing with aquatic Hemiptera, we are informed that without exception they are predatory: those which dwell upon the surface capturing such flies and other terrestrial insects as may chance to fall into the water, and those that pass their lives beneath the surface preying upon aquatic insects and similar organisms. In the light of recent observations along this line, the above information seems inadequate. Corixids for instance are largely herbivorous. The bulk of the food of our common waterstrider, Gerris marginatus, consists at certain times of the year almost exclusively of the Jassids and related forms that feed on Juncus and other plants bordering on and growing in the shallow waters. Our common species of Rheumatobates, while it does not disdain to feed upon small insects that fall into the water, obtains its main supply from the little crustacean forms such as Ostracods and Daphnians, which swarm the quiet pools. These it captures as they rest at the surface, scooping them out and holding them aloft upon the upturned tip of the beak, while the body of the little victim is being depleted of its nutritive material. A species of the genus Microvelia common in Kansas has access to the same source for its food supply and similar habits of consuming it. Mesovelia mulsanti, our little green Gerrid, has been observed exploring the sides of stems of Juncus and Typha that lay just beneath the surface for Ostracods, which they occasionally obtained, while the well-known marsh treader, Hydrometra martini, stalks about over the floating vegetation in search of whatever small beings chance to come to the surface film. Its victims have been observed to consist of mosquito wigglers, mosquito pupa, emerging midges, nymphal corixids, and Ostracods, as well as small terrestrial insects floundering on the water. Among the bugs that live in the water, none are more common than the back-swimmers, or Notonectids, and the water boatmen, or Corixids. The former feed in their first three stages largely upon the small crustaceaOstracods, cyclops and Daphnians, etc., adding to this diet such other forms as they are able to master, including corixids, mosquito larvæ and their own weaker brothers, while the source of the food supply of the boatmen2 is found in the brown, sedimentary material on the bottom of the pool. This they scoop up with the flat rakes of their fore-legs. These rakes are the somewhat spoonshaped terminal segments or pale, which are most admirably equipped for their work. An examination of the contents of the digestive tract reveals much of disorganized unicellular plant matter, diatoms, oscillatoria, euglenæ, chlamodomonas, and occasionally the shell of an arcella, or the remains of other lowly animal forms. Thus, it may be noted that the Corixids can be looked upon as members of the producing class in the waters where they are found. Gathering their food from the slimy ooze at the bottom of the pool, they in turn make forage for the many predatory animals that lurk in the shadowy places or dart in pursuit of their prey. We have witnessed their capture by Notonectids, Naucorids and nymphal Belostomas, by the larvae of Dyticids and Gyrinids, and are forced to believe that they take their place with the Entomostraca in furnishing food supply. Their alertness and agility, however, permit them to maintain themselves even in waters swarming with carnivorous forms, while in proper waters, with an absence of a dominating predatory population, they thrive in astonishing numbers. More might be said concerning the rôle played by the aquatic Hemiptera in the society of water forms, but this will suffice to indicate that they have a part not heretofore recorded-an intimate relation to certain of the 1 We have reared N. undulata to end of fourth instar in a small Petri dish, its only food being ostracods supplied to it daily by means of a pipette. 2 We have carried a species of boatmen through its entire cycle as many as twelve individuals in a single Petri dish upon such fare. Entomostraca, and even to the unicellular life of our ponds and pools. H. B. HUNGERFORD CORNELL UNIVERSITY THE DOCTRINE OF EVOLUTION AND THE TO THE EDITOR OF SCIENCE: In the minds of those who are beginning to be classed among the older men, there still lingers the memory of the time when the pulpit hurled its denouncements against those men of science who had the temerity to accept the doctrines of evolution as advanced by Darwin and Huxley. An interesting instance of the entire change of opinion that has come over the clergy is shown by an experience that occurred at the exercises connected with the celebration of the one hundredth anniversary of the consecration of St. John's Church in Washington City on January 14, 1917. A former rector of St. John's, the Rev. Dr. George William Douglas, now a canon of the Cathedral of St. John the Divine in New York City, in a sermon in which he reviewed the history of the church, spoke of a century as being a very short time in comparison with the time during which man had inhabited our earth, quoting Henry Fairfield Osborn's recent work on "Men of the Old Stone Age" as his authority, for the number of years. It is a far cry to the Oxford meeting of the British Association in 1860 when the learned Bishop Wilberforce attempted so unsuccessfully to controvert Huxley, the youthful advocate of science, then well nigh unknown outside the narrow circle of scientific workers. On Huxley's tomb are these words: And if there be no meeting past the grave, Future visitors to the burial place [of Huxley] on the northern heights of London, seeing on his tomb the above lines, will recognize that the agnostic man had much in common with the man of faith. It is interesting to note the fact that Osborn was a pupil of Huxley's and by chance was in the congregation when Dr. Douglas preached his sermon. MARCUS BENJAMIN THE MANUFACTURE OF APPARATUS AND CHEMICALS TO THE EDITOR OF SCIENCE: It has often occurred to me that it would be beneficial to science if some of the large universities of this country would cooperate to build a factory where chemicals and apparatus would be manufactured and sold to the various scientific institutions at a correct margin of profit. Perhaps the Rockefeller or Carnegie Foundation could be interested in such a project. The majority of fellow investigators and university professors would welcome such an arrangement, for it would make material accessible which is difficult to obtain otherwise and might be an important source of instruction to industrial chemists and physicists. LOUIS BAUMANN THE STATE UNIVERSITY OF IOWA LORD LISTER ON THE VALUE OF VIVISECTION TO THE EDITOR OF SCIENCE: In reference to the letter from Lord Lister to myself published in SCIENCE of March 30, 1917, I beg leave to make this explanation. Recently the original copy of this letter has been found. It is dated 12 Park Crescent, Portland Place, London, West, 4th of April, 1898, and addressed to myself. Just after its receipt I handed it to a friend to use in connection with the hearing before the United States Senate on the Gallinger Bill relating to animal experimentation in the District of Columbia. My friend presented it at the hearing and it is published in the pamphlet relating to that hearing. When Sir Rickman Godlee sent me a copy of the "rough draft" of this letter not long ago, saying if it had been received he would like to publish it in his "Life of Lord Lister," I went with great care over all of my letters and could not find the original. As it was almost a score of years since it had been received I had quite forgotten it and came to the conclusion that either it had gone astray in the mails or had never been sent. It has been returned to me and I have placed it in the Library of the College of Physicians of PHILADELPHIA, PA., March 31, 1917 QUOTATIONS THE AMERICAN ASSOCIATION AND WORK IN AGRICULTURE THE annual meeting of the American Association for the Advancement of Science is one of the great scientific events of the year. It is a vast clearinghouse for ideas and results in science, and for the testing and molding of views. It presents the largest forum in this country for healthy, tempered but searching criticism in science, without which science becomes self-complacent, lax and unexacting in its requirements. Beyond this, such a meeting of men associated with the various branches of science has a remarkably broadening influence. One gets new insight, suggestion and inspiration from such a contact of minds, such a presentation of evidence, such a weighing and testing of results and of views. The individual finds anew that his branch of science or his specialty has relations beyond the narrow limits in which he has been considering it, and that there is not only an interest in following this broader relation, but a danger unless he does that he may specialize too closely in his thinking and view his subject out of focus. Hence it seems worth while for the man of science to foregather from time to time with his colleagues in the annual convocation, worth the time and worth the money outlay. This is not so much to listen to papers which might be read or to present a report which might be published, but to keep his mind from narrowing, to maintain a contact with science which is well nigh impossible otherwise, and an association which contributes so much to the zeal and the satisfaction of a scientific career. It brings him definitely into membership in that great fraternity of workers in the broad field of science some for its own sake, some for its relations to human welfare, all having the common purpose to advance knowledge and understanding. It was the belief in such advantages that led thousands of men and women to jour ney long distances, many from the south and the west, to attend the New York meeting. The relation to agriculture of considerable parts of the programs of various sections and affiliated societies seems increasingly greater with each succeeding meeting. Perhaps it is because our interest is broadening. Perhaps it is because the investigation in agriculture is leading more and more deeply into the realm of the sciences. And undoubtedly it is because interest in these problems is becoming more widespread, for the problems of agriculture are now attracting the attention of very many men and women identified with nonagricultural institutions. The biological chemists, the various botanical organizations, the entomologists, the zoologists, the geneticists, the ecologists, all had papers of immediate import to agricultural investigation. Indeed, there were so many of these contributions and discussions that the difficulty was to hear more than a small part and to make a selection.-Experiment Station Record. SCIENTIFIC BOOKS Plant Succession. An Analysis of the Development of Vegetation. By FREDERIC E. CLEMENTS, Carnegie Institution of Washington, Publication Number 242, Washington, D. C., 1916. Pp. xiii + 512, 61 half tone plates of two to three figures each, and 51 figures in the text. For nearly a quarter of a century the author of this large and attractive volume has been investigating numerous problems in the field of phyto-ecology and related subjects as he has found them in the great out-of-door laboratory of western United States. This area is particularly stimulating for such work since so many of the natural life phenomena have been preserved to the present in nearly their original conditions. During these years the author has been favored with unusual facilities for the conduction of his investigations. Because of these facts, as well as because of the well-known leadership which American ecologists enjoy, this latest work from Clements will attract the attention of botanists and biologists in general throughout the world. The reader must understand that this work is not in any sense a treatise on general plant ecology. It represents a careful examination of the facts and principles of plant succession, an analysis of the development of vegetation in the past as well as the present, together with a digest of the methods for investigating successional phenomena. The subject-matter of the monograph is arranged in fifteen subdivisions or chapters. In Chapter I. the author rewrites his rather familiar views as to the fundamental nature and causes of succession. He points out that "the developmental study of vegetation rests upon the assumption that the unit or climax formation is an organic entity." As a living entity this unit arises, develops, matures and eventually disappears. All such entities or formations develop as a result of succession which may occur again and again in the history of each climax unit. The most striking external feature of succession lies "in the movement of populations, the waves of invasion, which rise and fall through the habitat from initiation to climax." An excellent historical summary beginning with King (1685) and including the work of twentieth century ecologists is included in Chapter II. This is a valuable summary of the concepts that have helped in shaping modern ideas with regard to plant succession. Then follows a long chapter on the causes of succession. "Initial causes "" are discussed under the captions: Topographic Causes, Erosion, Deposit, Elevation and Subsidence, Edaphic Causes, Climatic Causes, Biotic Causes, while "ecesic causes are enumerated as Aggregation, Migration, Ecesis, Competition and Invasion. This chapter is followed by a study of stabilization and the development of the final or climax community. The structure and units of vegetation are treated at length and the views of various ecologists upon these subjects summarized. One of the most interesting, as perhaps most valuable, parts of the book is the attempt of the author to focus attention more sharply than has ever been done before upon the fact that plant communities may and should be classified by means of seral units as well as by climax units. Both methods have been used by various investigators rather indiscriminately, or at least no particular model (if there be such) has been followed consistently. Clements rightly emphasizes the desirability of working out and adopting a set of terms to cover these two concepts of vegetation and he goes so far as to propose terms by means of which the various climax and seral features of the plant formation may be described. The reviewer is aware of the advantages and disadvantages of the various systems which have been proposed in the past and we must confess that this latest proposal is perhaps still far from the ideal, and yet it represents an advance, it marks progress. At least it serves to focus the attention upon the dynamic phases of vegetation as apart from the static. The author may be criticized for the introduction of new terms in this connection, but new concepts or relations may be expressed only by appropriate words. Scientific men should not be confounded by the introduction of an occasional new term. The climax units which Clements proposes are: associations, climax communities which associated regionally constitute the formation; consociations, the units of the association, characterized by a single dominant species; societies, communities within an association or consociation controlled by one or more subdominant species; and clans or aggregations of secondary species within either of the above subdivisions. The clan is quite local and often not sharply delimited from the society. Seral units are analogous to climax units or communities throughout the course of succession. These units are proposed in order to point out sharply the distinctions between the developmental or dynamic and climax or static phases of vegetation. The associes is the developmental equivalent of the association, differing from the latter only in its transient nature. The consocies corresponds to the consociation in the same manner that associes corresponds to association. "The consocies is a seral community marked by the striking or complete dominance of one species, belonging, of course, to the life-form typical of that stage of development." The socies is likewise the developmental equivalent of the society. The colony is an initial community of two or more species. Colonies resemble clans in their limited size and absence of clearly defined relation to the habitat. From their appearance in bare areas colonies are nearly always sharply delimited. The invasion of weeds frequently follows the colony type of grouping. The family is a group of individuals belonging to one species. Because of this nature families are quite rare in general, but they are common in bare areas and in the initial stages of a succession. This attempt to work out a classification of vegetation types founded upon the developmental basis should appeal to all broad-minded students of plant ecology. Another valuable portion of Clements's book is the part devoted to the climax formations of North America as summarized from the available literature. Successional studies in Eurasia are also ab stracted. An extended portion of the monograph is devoted to a discussion of "past climates and climaxes" or to the succession of vegetation in remote times as revealed in the geological record. "The operation of succession was essentially the same during the geological past that it is to-day: from the nature of their vegetation forms, the record deals largely with the ultimate stages of such successions. It is evident that geological succession is but a larger expression of the same phenomenon, dealing with infinitely greater periods of time, and produced by physical changes of such intensity as to give each geological period its peculiar stamp. If, however, the geological record were sufficiently complete, we should find unquestionably that these great successions merely represent the stable termini of many series of smaller changes, such as are found everywhere in recent or existing vegetation. . . . In short, the development and structure of past vegetation can be understood only in consequence of the investigation of existing vegetation." |