Let us consider some of the factors which are most apt to disturb or distort the work of reason.

First and foremost is the love of one's own observations and opinions. If it takes the form of pride, which leads us to be so careful that our opinions deserve trust, well and good; but if it is merely an excitable vanity, it lures us to disaster. Think of the innumerable controversies of science, and tell me how often have the disputants cared less to prove themselves right, than to ascertain the truth, be their own opinions right or wrong. What we strive for and, I fear, never attain is perfect indifference to the sources of an idea. It is almost impossible not to feel an undue interest in our own idea, yet such an interest inevitably leads to overvaluation of the evidence in favor of our idea, and undervaluation of the evidence against it. Let us, therefore, avoid polemics, and so avoid the temptation to search for proof of a personal theory, when we ought to search for the truth only. Never let a pupil say: "I am sorry it did not turn out thus and so; it would have been so fine if it only had been so." Let him be glad at discovering the truth. When he is eager for controversy, teach him the difference between discussion and controversy, and keep him out of the latter. Point out to him that erroneous conclusions are to be set aside, not so much by disproving them as by demonstrating the true conclusion. Darwin's theory of pangenesis has been set aside, not by being disproved, but by the demonstration that the theory of germinal continuity is well founded. The cataclysmic theories of Adam Sedgwick and the older geologists have been overthrown by the accumulated proofs of the gradual character of geologic changes. An error is hard to kill, but with a truth you may drive it away; therefore research is better than controversy.

The love of one's own opinion is the most insidious and fruitful of all sources of human error, and accordingly we recognize vanity and self-conceit as the gravest of defects in the naturalist's character. It is easier to make a competent investigator out of a dull man than out of a conceited man.

A second source of error is impatience-impatience to get results before the data are sufficient to support conclusions. What a horrible record against this century has been piled up by the accumulation of "preliminary notices," "vorläufige Mittheilungen, and notes préventives!"-a vast mass of mistakes, a terrible impediment to science, and all to gratify the mad longing for priority. I wish that the publication of a preliminary notice to secure priority should disqualify for membership in this society, and I trust that every one of us will stand firmly and sternly against this abuse, which is doing more to degrade science than any other influence I know of. Indeed, I am almost ready to say

that the Académie des Sciences at Paris has done more against science than for science, because in its Comptes-Rendus it initiated the custom of brief premature publication for priority.

A third difficulty in the way of reason is the tendency to speculate. The annual waste of cerebral protoplasm in speculation must amount to millions of pounds. A vast generalization has its allurements, but in yielding to them we are apt to be drawn away from the actual facts. There is another danger, for the mere lapse of time gives hypotheses a dignity and apparent worth, and it were easy to give illustrations. You are doubtless all familiar with the hypothesis of panmixia, which was advanced on the flimsiest of bases; yet a few years later its propounder treats it as an established law. The like misfortune might happen to any of us, since it is easy to remember the conclusion and to forget the evidence. Among zoologists speculation has long been rife, and for many years we have been deluged with phylogenetic inferences, with the evil accompaniment of eager welcome for facts which agree with the favorite phylogenetic theories of the day, and of disdain for such facts as did not concord with these theories. Thus has been created that biological mythology against which Prof. E. B. Wilson has protested so suitably.

Philosophy and science are practically often incompatible-not because philosophy is unworthy of our entire respect, but because would-be philosophers are not seekers for wisdom but lovers of speculation. Twenty years ago we thought that Oken, whose Natur-philosophie was created by his speculative enthusiasm, would never have another imitator, but since then biological speculation has become almost a fetich. Let us part company from the horde of foolish thoughts which have too long masqueraded under the false garb of philosophy. For our lifetimes the labor of inductive research will suffice, and we may well leave deduction for future generations. Philosophy, so called, is often an effort to decide what must be, but while knowledge remains imperfect the "must be's" will guide us wrong more frequently than they will guide us aright. As long as Science seeks to determine what is, her work will endure. My protest against speculation is no idle rhetoric, for the evil is very great. I hope that Weismann's mystical treatise on Germplasm will prove to be the culminating effort of the speculative school, and that the influence of the school will be as brief as it has been widespread.

A hypothesis may be a good serving maid to clean away rubbish and get the workroom in order. It is for us to remember that this good maid makes the worst mistress.

There are many other difficulties of character which obstruct reason, but you will excuse me from an exhaustive review of them, and therefore I will refer only to one more, and that briefly.

I mean the artistic perception which induces us to look for completeness, clearness, and simplicity, so that we are tempted to add a little or more to our conclusions, or to accept a result partly because it is complete, clear, and simple. The most eminent illustration of this tendency is Herbert Spencer, whose mental processes are so far governed by his love of clear, simple formulæ that he uses simplicity as a test of his conclusions, and makes formulation a test of truth and a substitute for proof. We are all inclined to be lax as to our proofs if the generalization is satisfactory and pleasing, but Spencer's mistakes may warn us against the danger of gratifying this inclination. Science is not one of the fine arts. Its work can not be directed by the love of beauty or by sentiments. Science is a pursuit for the intellect and for the intellect alone.

I will turn to another part of our work-publication. Scientific publications naturally group themselves in four classes: original memoirs, handbooks, text-books, and bibliographies. Now in the three latter good workmanship is indispensable, for their utility depends on their arrangement, the right proportion of parts, and the skillful use of language; but the value of original memoirs depends upon the discoveries which they report and the sufficiency of the evidence presented to support the discoveries claimed; hence the form in which the matter is presented appears less important than in a handbook or text-book. Moreover, our original memoirs, saving a very few which mark epochs of progress in natural science, are, as we all perfectly know, destined to oblivion. In time our new discoveries will become old-established facts, the original authorities for which will be forgotten. Who of us would search, save as a student of the history of science, for the original authority on the muscles of the human arm, or for the proof that fossils are not lusus naturæ but genuine remains, or that some rocks are of sedimentary origin? When we have attained certainty in our discoveries, they gradually become so verified that the memoirs, which originally brought the proofs, lose their value. Original memoirs are like digestive organs; they are filled with raw facts, which they prepare for assimilation, but to build the body of science these same facts must be absorbed and transmuted.

We are, of course, convinced that our original memoirs are for temporary service, though their recorded facts are to be permanently added to knowledge. To the influence of this conviction we may ascribe that carelessness of style, verbosity, and frequent padding which mar scientific writings too commonly, because the necessary care does not appear worth while for a temporary essay. But the time has now come when the burden of reading the thousands of pages of memoirs which are published annually

even in a single field of research is overwhelming, and it is evident that for the advantage of science every legitimate means to lessen this heavy burden should be adopted. The habit of conciseness and clearness should be sedulously cultivated.

With a view of estimating what might be done in this direction, I have gone over a number of articles upon embryology which have been published in the four accepted languages of science-German, English, French, and Italian-during the last two years. I am compelled to admit that the majority of these articles could be easily shortened by a half, and many of them shortened by much more than that, and still offer a thorough, or, better, said an exhaustive account of the matter presented. I have been astonished at the amount of perfectly irrelevant matter and of personal details which appears. The author informs us that he could not leave home until Tuesday; that it rained on Friday; that he had to carry the eggs eleven kilometres on Saturday; that he used Delafield's hæmatoxyline solution, of which he gives the formula; that he began making his sections with a Thoma microtome, but later used a Schanze, as Prof. X-needed the Thoma; the author's work was interrupted because he was called home on account of his father's illness; his father lived in Meyerstadt or Smithville. What have these and thousands of similar items to do with the plane of the first cleavage of the ovum, the origin of the centrosome, or the development of the notochord, or any other problem of embryology? I have not invented my illustrations; on the contrary, I have taken them from some of the best of recent embryological articles. Similar illustrations. can be collected from recent literature of any branch of naturalhistory research.

So far as embryological literature is concerned, the French standard is certainly the lowest. Their verbosity is infinite, and one must read page after page for a single fact. Many of the French memoirs I have read are literally ten times too long for the matter. Next to the French come the Germans and ourselves -Americans-who, in the biological sciences, are disciples of the Germans. The best-written memoirs are the English, owing, I think, to Huxley's influence. Huxley has carried scientific writing to unsurpassed excellence, combining clearness and brevity in a marvelous way, and his pupils, Francis Balfour and Michael Foster, have invariably sustained a high literary standard. Their example has been all the more telling because literary art holds the same position in England that music holds in Germany and painting in France.

No doubt the ark of science will traverse the deluge of publication safely and land us on the Ararat of natural law, but I fear our Ararat will not appear until the deluge subsides.

But I must hasten to the second part of my address.

II. THE EFFECT OF THE NATURALIST'S CAREER ON HIS CHARACTER. The occasion does not permit me to refer to more than two or three professional traits.

The best that we gain from the pursuit of research is, I believe, our characteristic optimism. We are engaged in achieving results, and results of the most permanent and enduring quality. A business man may achieve a fortune; but time will dissipate it. A statesman may be the savior of a nation; but how long do nations live? Knowledge has no country, belongs to no class, but is the might of mankind, and it is mightier for what each of us has done. We have brought our stones, and they are built into the edifice and into its grandeur. My stone is a small one. It will certainly be forgotten that it is mine, nevertheless it will remain in place.

How different is the pessimism toward which literary men are seen to tend! Harvard University lost James Russell Lowell in 1891, and Asa Gray in 1888. The letters of both of these eminent men have been published. Lowell's letters grow sad and discouraged, and he gives way more and more to the pessimistic spirit. Gray is optimistic steadily and to the end. The difference was partly due to natural temperament, but chiefly, I think, to the influence of their respective professions. The subject material of the literary man is familiar human nature and familiar human surroundings, and his task is to express the thoughts and dreams which these suggest. He must compete with the whole past, with all the genius that has been. There is nothing new under the sun, he exclaims. But to us it is a proverb contradicted by our daily experience.

The attitude of literary men is indeed sad. Lowell opens his essay on Chaucer with the question, "Can any one hope to say anything, not new, but even fresh, on a topic so well worn?" and answers, "It may well be doubted." This feeling that anything new is impossible is not modern. La Bruyère begins his Caractères with "Tout est dit, et l'on vient trop tard depuis plus de sept mille ans qu'il y a des hommes, et qui pensent"; and two hundred years later Joubert repeats: "Toutes les choses, qui sont aisées à bien dire, ont été parfaitement dites; le reste est notre affaire ou notre tâche: tâche pénible."

Another trait which is very striking shows itself, not in all naturalists, but in nearly all great naturalists—the trait of humility-not the humility of self-depreciation, but the humility which is the privilege of those who pursue a high ideal. The great naturalist cares for the absolulely true, and, though he may know that he is abler than other men, he feels only a minor interest in personal comparison, and measures himself by a different stand